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PresidentW. R. Paylen, Calif.
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1970-1973: Lottie Cave, Wm. Dunbar, Elmer Lorenz, Edward McWilliams, Patrick Mitchell, Eric Knobloch, Kelsey Williams.

1971-1974: David H. Benzing, Fritz Kubisch, George Kalmbacher, Wilbur Wood, W. R. Paylen, Kathy Dorr, Amy Jean Gilmartin, Bea Hansen.

1972-1975: Jeanne Woodbury, Ralph Barton, George Anderson, Virginia Berezin, Victoria Padilla, Charles Wiley, Ervin Wurthmann, Jean Merkel.


Adda Abendroth, Brazil; Luis Ariza Julia, Dominican Republic; David Barry, Jr., USA; Olwen Ferris, Australia; Mulford B. Foster, USA; Marcel Lecoufle, France; Harold Martin, New Zealand; Richard Oeser, Germany; Dr. W. Rauh, Germany; Raulino Reitz, Brazil; Walter Richter, Germany; L. B. Smith, USA; R. G. Wilson, Costa Rica; J. Marnier-Lapostolle, France.


Published six times a year: January, March, May, July, September, November. Free to members.

Editor: Victoria Padilla
Asst. Editor: Kathy Dorr


The Men Behind the Scene—Dr. Werner Rauh
  Victoria Padilla83
The Bromeliads at Heidelberg
  Victoria Padilla87
Some Remarks on the Water Supply of Bromeliads
  Werner Rauh, Rainer Schill, Nesta Ehler and Wilhelm Barthlot89
An Unfinished Inflorescence
  George Kalmbacher112
Why are Some Bromeliads Less Than Perfect?
  Edith Meyer115
A Method for the Aseptic Culture of Tillandsia Seed
  Guy Wrinkle117


Guzmania lingulata var. lingulata — Photo by M. Lecoufle

Articles and photographs are earnestly solicited. Length is no factor. Please mail copy and all questions to the editor, 647 South Saltair Ave., Los Angeles, California 90049.

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No one will deny that one of the foremost figures in the bromeliad world today is Dr. Werner Rauh of the Institute of Systematic Botany of the University of Heidelberg. Botanist, horticulturist, professor, photographer, writer, explorer, raconteur—he is a man of many talents, any one of which would make him outstanding. His energy is boundless and may well put the average man to shame. How he can do so much and do it so well is a wonder to all those who know him.

He was born in Germany in 1913 and studied biology in Leipzig, Innsbruck, and Halle. In 1939 he joined the University at Heidelberg and in 1965 was made director of the Institute of Systematic Botany and its botanical garden, which in the short space of eight years he has made into a mecca for plant enthusiasts the world round. His special interests are the cacti and succulents of the Old and the New World, orchids, and bromeliads. In 1971, Dr. Rauh hosted the Eleventh Congress of the International Organization for Succulent Plant Study, and those who attended were amazed at the magnificence and variety of plants in the many greenhouses. All agreed that the succulent collection, as well as the bromeliad collection, is unquestionably one of the finest in the world.

The botanic garden has been enriched greatly by Dr. Rauh's many plant collecting expeditions. These include: 1954—Peru and Ecuador, 1956—Peru, 1959—Madagascar and East Africa, 1961—Madagascar and South Africa, 1963—South Africa, 1965—Arabia, 1967 —Peru, 1969—Madagascar, 1970—Peru, Baja California, and Mexico, 1971—Peru and North and South Mexico.

It was while collecting cacti and succulents in South America that Dr. Rauh became interested in bromeliads, especially the gray-leaved tillandsias, many of which live in the same habitat as cacti. His collection of tillandsias from the Peruvian Andes is without equal.

Werner Rauh manages to find time between his teaching and traveling to contribute generously to the publications of the cactus and succulent societies and to The Bromeliad Society. Many members are the proud owners of his Bromelien fur Zimmer und Gewachshaus published in 1970. The second volume will be out shortly. All his writings are profusely illustrated with his photographs, which for clarity and artistry are superb. As said previously, everything that Dr. Rauh does is with the sure hand of an expert.

From his many collecting trips, Dr. Rauh has brought back many bromeliads new to horticulture. Three of these have been named in his honor by Dr. Lyman B. Smith: Tillandsia rauhii, Puya rauhii, and Vriesea rauhii—all from Peru.

Hilde and Werner Rauh in Santa Barbara, California

Puya rauhii, L. B. Smith, growing in the Cordillera Blanca of Peru at 3,500 meters.



The Tillandsia Section. The plants are bound on to the rootstocks of grapes.

Vrieseas, guzmanias and other epiphytes growing on post.

Connected with the University of Heidelberg in Germany, but some distance away from the renowned campus, is the Institute for Systematic Botany, where is housed one of the world's outstanding bromeliad collections. This is a fairly new addition to a university whose beginnings date back several centuries, the splendid gardens, laboratories, classrooms, and offices, as well as the elaborate complex of 26 glasshouses, radiating from a large central conservatory, being only a dozen or so years old.

Two of the glasshouses are devoted entirely to bromeliads, which must, at this writing, number well into the thousands, thanks to the indefatigable efforts of the director, Dr. Werner Rauh, to acquire as complete a collection as is possible. Dr. Rauh is in constant contact with growers and collectors throughout the world, and for the past several years, he and his wife have made extensive collecting trips to South America in search of new species. Dr. Rauh has a special affinity for tillandsias, and he has scoured the Andes in search of new species. Every year sees at Heidelberg bromeliads new to cultivation, and many still remain to be identified.

As can be seen from the accompanying photographs the bromeliads are grown as nearly as possible as they exist in their native habitat. The tillandsias are all mounted (by means of strips of nylon hose) to pieces of natural wood and hung as close to the top of the glasshouse as is possible in order to get maximum light and air circulation.

The xerophytic bromeliads are grown directly in beds in the concrete benches, with rocks and sandy, loose soil to simulate their natural growing conditions. Although such plants are usually difficult to grow under greenhouse conditions, these appear to be thriving.

Guzmanias, vrieseas, aechmeas, neoregelias, and other epiphytes are either grown directly in beds in the benches or fastened to logs or posts, depending upon the growing habit of the bromeliad in question. The beds are filled eight to ten inches with a light, loose medium that provides the maximum degree of drainage and aeration. The plants are grown close together to simulate jungle conditions. The beds have bottom heat.

During June, July, and August, a number of the tillandsias and hardy species are brought outside into the garden where they can enjoy the sun and the occasional summer rains.

The Heidelberg collection is not open to the general public.

The Xerophytic Section with tillandsias above.

Guzmania section



Fig. 1 Tillandsia usneoides in the glasshouse at Heidelberg

For a long time it has been a well-known fact that many bromeliads do not absorb water and nutrients through their roots but use their leaves for this function. Therefore, some bromeliads are completely rootless, as in the case of the widespread Tillandsia usneoides, (Fig. 1) which hangs in long thick strands from trees, rock walls, and even telephone wires. It is seldom grown from seed being easily propagated in a vegetative manner, every single strand producing a new plant. Only seedlings of T. usneoides disclose any root system, and it is poor and short.

Figure 2 — Puya raimondii

Bromeliads fall into two major groups: the terrestrial and the epiphytic.

The representatives of the first group belong mostly to the sub-families of the Bromelioideae and Pitcairnioideae: Puya (Fig. 2), Pitcairnia, Hechtia, Dyckia, Orthophytum, Navia, Ananas, Pseudananas, Bromelia, Deuterocohnia, and others. They are all earth plants and possess a perfect and fully developed root system. (Fig. 3) These roots not only have the function of firmly fixing the plant in the substratum, but they guarantee a supply of water and necessary minerals.

Figure 3 — Puya raimondii

The second group, the epiphytic bromeliads, however, grow mostly on trees or on rocks, seldom on the ground. Only the Peruvian desert tillandsias, such as T. paleacea, T. straminea, T. purpurea (Fig. 5), T. latifolia (Fig. 5) grow as terrestrials in pure sand in the coastal deserts as well as epiphytes on trees in the more inland dry forests. But the root system of these terrestrial desert specimens is very poor, and most of the elongated stems are nearly rootless as in T. werdermannii (Fig. 4). The plants can exist without roots, because these desert Tillandsias belong (as well as the epiphytic ones) to the biological group of "atmospheric" Tillandsias (see later). They live exclusively from the humidity of the air, which they absorb by help of their leaves. The roots are therefore of no importance to this group of bromeliads. Indeed, the Peruvian coastal desert is a "mist-desert." For nearly six months of the year it is covered with mist, which reaches up to an altitude of about 1,500 feet, called in Peru "garua." Although there is seldom any rainfall in this desert south of the 4th degree of latitude, the air contains a humidity of 90 percent and more. This is the reason why Tillandsias cover miles and miles of the pure sand southwards to the border of Chile. (Fig. 4) They grow in clumps (Fig. 5) or form long strands (Fig. 5) in which the living "heads" all point together in the same direction, namely to the sea shore, (Fig. 5) from which comes the sea wind charged with high humidity. Those stems and leaves which do not get this wind eventually die. (Fig. 5)

Figure 4 — Tillandsia werdermannii

Figure 5 — (above) Tillandsia purpurea; (below) Tillandsia latifolia

Figure 6 — Tillandsia rauhii

Epiphytic bromeliads belong mostly to the following genera: Aechmea, Billbergia, Canistrum, Nidularium, Wittrockia—all of the subfamily Bromelioideae, and Tillandsia, Vriesea, Guzmania, Catopsis of the subfamily Tillandsioideae. Most of the species of these genera have a well developed system of roots, but these acquire other functions than those of normal earth roots. Their main function is to attach the plant to the bark of trees or surface of rocks (Fig. 6) with a kind of cement which they produce on their underside. The water is absorbed exclusively by the leaves.

Epiphytic bromeliads now can be divided into two groups: the so-called green and the gray or white bromeliads. They do not differ only according to their areas of distribution, but also by their growth forms. The first group is represented by rosette-plants: their stems are short and stout, and the numerous leaves form a funnel-shaped rosette of sometimes enormous dimensions (up to 2m as in the case of Vriesea reginae, Tillandsia maxima, T. rauhii, and others. (Fig. 6) The leaf sheaths are well developed and arranged in such a manner that all together they form a sort of tank or aquarium, filled with water which cannot run out. This aquarium is the "life-room" of a very specialized microflora and fauna (including frogs and snakes); the water serves as a reservoir for dry, rainless periods. It will be absorbed by intricately formed trichomes, which cover the surface especially of the leaves' sheathes in a more or less dense cover, whereas the leaf-blades bear only few trichomes, especially beneath. In many species only the young leaves are covered with a dense cloth of trichomes; they become glabrous with age. The blades of other species are covered with thick layers of wax (some Tillandsia species and Catopsis and look chalky white.

The areas of the green bromeliads with funnelform, water-storing rosettes are steep rockwalls of dryer regions, the mist forests of high altitudes, and the rain forests of the lower altitudes. Relatively few species grow on trees in dry forests with deciduous leaves and low rainfall.

Figure 7 — Tillandsia cauligera

Figure 8 — Tillandsia argentea

The second group of epiphytic bromeliads consists of the so-called white or gray bromeliads, especially members of the genera Vriesea and Tillandsia. They are all inhabitants of dry, rainless regions, with a high air humidity like that of the Peruvian coastal desert, or dry forests with low precipitation. Here the bromeliads are often associated with big cacti. As these bromeliads live only from the humidity of the atmosphere, they have been called by the famous German botanist A. F. W. Schimper (1888) "atmospheric" bromeliads. Their stems are mostly elongated (Fig. 7); if they are short and the leaves are arranged in a rosette, their sheathes form an onionlike water-storing bulb, as in Tillandsia argentea (Fig. 8) T. filifolia, T. plumosa, and others. Some of the atmospheric bromeliads, such as T. usneoides, T. duratii, and T. decomposita, are completely rootless. They don't need roots because they absorb the humidity by the help of their leaves. These are covered with a very dense cloth of trichomes of a complicated structure. These are true organelle, which guarantee the water supply and are also responsible for the gray and white color of the leaves and stems; the trichomes include air between them (when dry) on which a total reflection of light takes place. We notice the same physical phenomenon in fresh fallen snow; the more air there is between the snowflakes, the whiter is the color of the snow.

Figure 9

To explain the function of bromeliad trichomes, we have to make a microscopic study and take as example a trichome of a Vriesea species. Fig. 9 shows such a trichome, and from it one can see its very regular arrangement of cells. The center is formed by a group of 4 right-angled cells (C), called central-cells; these are surrounded by a ring of 8 cells, the ring-cells. Both cell groups together form the disk or central shield of the trichome. This itself is surrounded by 32 long stretched wing-cells with thick walls. We will see later that this cell sequence 4—8—32 can vary.

The function of such a trichome can be understood only by making a longitudinal section through it, that means a cross section through the leaf blade itself (Fig. 9, II, III). In such a section the trichome resembles a tack, and it is composed of two main parts, the "cap" and the "stalk." The cap is formed by the wing and the shield-cells. These are dead and their lumens are filled with air when dry. The stalk is formed by a row of living, water-absorption cells, (Fig. 9, I-III, A) which are sunken into the parenchyma of the leaf, with which the stalk is connected by a basal cell group, the so-called foot-cells. (Fig. 9, II, III, F).

The upper cell of the stalk has a special name and according to its shape it is called dome or middle-cell (Fig. 9, II, III, D).

According to the fundamental investigations of C. Mez (1904) the trichomes of bromeliads operate after the principle of a water-pump. He speaks therefore of "trichome-pumps." The details of the mechanisms of water absorption are not yet known, but the trichome works in principle as follows:

When the air is dry, when there has been no rain or dew for a long time, the anticline cell walls of the central shield are folded like an accordion (Fig. 9, II). Brought into contact with water, the wing cells absorb it quickly. The cell walls of the central shield begin to stretch and the cells enlarge their volume. Through osmotic action, water is drawn down over the dome cell into the living stalk cells and by help of the foot cells into the surrounding leaf parenchyma; from there it is transported to a special tissue, where it can be stored (Fig. 8, right). In consequence of the water absorption, the air between the leaf epidermis (Fig. 9, II, III, Ep) and the trichome-wing is replaced by water; therefore the cap of the trichomes becomes transparent and the green color of the chlorophyll of the leaf-plastids appears. When you spray a bundle of Tillandsia usneoides with water, you may notice that the gray-white color of the stems and leaves become green. The wing cells are working like a piece of filter paper which sucks off the water when it comes into contact with it. But more investigation is necessary to find out how mineral substances are supplied in the rootless, extreme atmospheric bromeliads.

According to the very detailed research of M. Tietze (1906) there exists a remarkable variability of structure in bromeliad trichomes, from simple, irregular to intricate and regular. We can establish an evolutional lineage, and with its help we can draw conclusions as to the water supply in general and to the phylogenetic development of the family in particular.

Following is a series of bromeliad trichomes photographed with the Stereoscan 600 electronic microscope1. We believe that you will agree that these are much more instructive and impressive than photographs taken with a normal light microscope. (See article of Mary L. Brown, "Bromeliad Trichomes," Journal of the Bromeliad Society, XXII, 5, p. 11-118.)

According to C. Mez and L. B. Smith, the Pitcairnioideae is the most primitive subfamily, and it was from it that the Bromelioideae and the Tillandsioideae have derived. In Fig. 10-15 we show the trichomes of typical representatives of the Pitcairnioideae, indicating a progressive tendency in trichome structure. Pitcairnia atrorubens has very simple and irregular trichomes. They consist of only one central cell from which radiate several elongated free cell bands (Fig. 10). A higher type of organization is represented by Fosterella penduliflora. The trichomes also have only one central cell, but the cell bands, which are free and elongated in Pitcairnia atrorubens are much shorter and more or less united, forming an irregular star. (Fig. 11)

Hechtia (Fig. 12), Abromeitiella (Fig. 13), Deuterocohnia (Fig. 14), and Puya (Fig. 15) show within the subfamily the highest organization type. The central cell is surrounded by a variable number of ring-cells, which form the central disk and this is surrounded by several rings of more or less regularly arranged wing cells. We much conclude that this type of trichomes, because they are so numerous, form a dense cover which serve not only as a protection against high transpiration but also (up to a certain degree) act as water-absorption organelles. But more detailed research must still be done.

In many species, the trichomes are localized only on the lower side of the leaves; nearly all the representatives of this subfamily are terrestrials with a well-developed water-absorbing root system.

Many Puya species bear in their inflorescence a dense tomentum of hairs which can be easily removed. Photographs with the Steroscan-Microscope show that this tomentum, especially in Puya ferruginea, is formed by stellate hairs, which form a protection against strong sunlight and frost for the young flower buds (Fig. 16). This appears to be necessary, as most Puyas live in high latitudes over 13,000 feet.

Within the subfamily of the Bromelioideae we have a similar progression of trichome structures (Fig. 17-27). Orthophytum fosterianum (Fig. 17) has the most primitive trichomes, resembling those of Pitcairnia atrorubens. From one central cell radiate deeply divided cell-bands, which are rolled in when dry.

The trichome structure of Araeococcus flagellifolius and Hohenbergia augusta can be compared with that of Fosterella; the trichomes of Streptocalyx angustifolius (Fig. 20) an epiphytic ant-bromeliad, are similar to those of Hechtia tillandsioides (Fig. 12); the trichomes of Bromelia balansae, which are arranged in longitudinal rows (Fig. 21), Aechmea aquilega (Fig. 22), Cryptanthus racinae (Fig. 23), and Wittrockia superba (Fig. 24) belong to the same type and correspond with those of Abromeitiella, Deuterocohnia, and Puya.

Most of the above mentioned members of the Bromelioideae are terrestrials; only Streptocalyx longifolius and Wittrockia superba are epiphytic on trees or on rock walls.

The most highly organized type of trichome in the subfamily of the Bromelioideae is to be found in the epiphytic genera Neoregelia, Nidularium, and Aechmea (Fig. 25-27), whose leaf-sheathes form a water-storing rosette. In Aechmea chantinii (Fig. 27), especially, we find a cell arrangement, in trichome cap, which is similar to that of some Tillandsioideae. In the center there is a group of 4 right-angled cells which are surrounded by rings of 8 and 16 cells, forming the central disk. In comparison with the Tillandsioideae the outer wing-cells are irregularly arranged and not stretched.

This type of trichome carries over to the representatives of the Tillandsioideae, the highest developed subfamily in the phylogenetical sense. Their trichomes have the most regular cell arrangement, coming in a multiple of 2. In the most regular type there are 4 central right-angled cells, surrounded by rings of 8, 16, and 32 cells, forming the central disk. This itself is surrounded by 64 elongated wing or alae-cells. (Fig. 33) Thus we have a cell sequence of 4 + 8 + 16 + 32 + 64. But there are many variations; one or more of the cell rings can be omitted (Fig. 33).

A very simple (primitive) trichome structure can be found in Catopsis (Fig. 28), some Guzmanias (as G. lingulata, G. mucronata) and some Vrieseas (as V. modesta). The cell formula of the trichome is 4-8-32 (Fig. 28:33, I). The trichomes of Guzmania insignis are built up after the unusual formula 4-8-47 (Fig. 29); G. calothyrsus, G. lindenii, G. minor have the cell sequence 4-8-64 (Fig. 33, II). In many atmospheric Tillandsias we have the formulas 4-8-16-64 (Fig. 33, III), resp. 4-8-16-32-64 (Fig. 33, IV). Unusual also is the cell sequence in Tillandsia hildae: we count up to 7 rings of disk-cells (the 7th ring is often incomplete) and more than 100 very elongated and very small wing cells with a sculptured cell wall surface (Fig. 30). A similar sculptured effect is seen also in the wing cells of T. fasciculata. (See Fig. 14 in the publication of Mary L. Brown.)

It must be mentioned that the trichomes, especially the wings of many atmospheric Tillandsias, are of a centric or an eccentric shape (Fig. 31). The shape depends upon the position of the trichomes on the leaf blade. The trichomes from the middle of the leaf blade are centric, while the wings of the trichomes from the margins of the same leaf show an extremely eccentric shape (T. usneoides Fig. 31, T. plumosa, T. tectorum, and many others.) We call these trichomes "dewtongues," for they are able to absorb even traces of dew or air-humidity.

We are able to make an interesting observation by help of the Stereoscan Microscope concerning the water absorption in Tillandsia rauhii. This species forms large funnel-shaped, water-storing rosettes (Fig. 6). The adult leaf-blades are covered with only a few trichomes, which are embedded in a thick layer of wax (Fig. 32a). We can observe narrow channels in the wax connecting single trichomes with each other (Fig. 32b). We suspected that these channels serve for water transport and were able to prove our theory with the help of fluorescent substances.

Summary: When starting this article, we did not intend to give a phylogenetic evolution of bromeliads based on the structure of the trichomes. There is no doubt, however, that the trichome structure of bromeliads shows a clear evolution from terrestrial to epiphytic forms, and that with the transition from the one to the other life-form, the function of the bromeliad trichomes changes also. In the gray and white, partly rootless Tillandsias the trichomes have different functions from those in the big Puya raimondii, for example. Our main and special intention was to show how magnificent bromeliad trichomes can be, as demonstrated with the Scanning Electronic Microscope in comparison with the normal light microscope (See the richly illustrated article of Mary L. Brown, Journal of the Bromeliad Society, XXII, 1972, pp. 111-118).

—Institute of Systematic Botany and Plant Ge`ography of the University of Heidelberg,, Germany.

1) We are indebted to the Cambride Co. who provided us with an instrument for our use.


Literature (not cited in the article of M. L. Brown)

Mez, C. Physiologische Bromeliaceen—Studien I. Die Wasser Okonomie der extremen atmosphaerischen Tillandsien. Pringsheim Bot. Jahrb. XI, 1904.

Schimper, A. F. W., Bot. Mitteilungen aus den Tropen II, 1888.

Tietze, M., Physiologische Bromeliaceen—Studien III. Die Entwicklung der Wasseraufnehmenden Bromeliaceen-Trichome. Zeitschr. f. Naturwiss. Halle, 1906.


fig. 1Tillandsia usneoides (L) L., a rootless Tillandsia, cultivated in the Botanical Garden of Heidelberg.
fig. 2Puya raimondii HARMS, the biggest bromeliad near Carhuaz in the Cordillera Blanca of Peru.
fig. 3Puya raimondii HARMS with its root-system.
fig. 4Tillandsia werdermannii HARMS, a nearly rootless Tillandsia, covering square miles and square miles of the southern Peruvian desert near Arica right: a cushion taken off by Hilde RAUH.
fig. 5above: Tillandsia purpurea RUIZ et PAV.;

beneath: Tillandsia latifolia MEYEN, minor in the central Peruvian desert, forming long strands. All the living heads are showing in to the direction of the seawind.

fig. 6Tillandsia rauhii L. B. SMITH, a big epiphytic Tillandsia, growing in steep rock walls. The leaf-rosette forms a water-storing "tank". (Valley of the Rio Sana, type locality.)
fig. 7Tillandsia cauligera MEZ, a "white" species with elongated stems left: in habitat near Tarma central Peru (2000 m), right: a plant in flower.
fig. 8Tillandsia argentea GRISEB., left: a form with short and thick leaves from Chiapas (Mexico).

right: a longitudinal section through the "bulb"; the leaf-sheathes form a water-parenchyme.

fig. 9Vriesea spec. I trichome in view from above II-III longitudinal sections through the trichome. II in dry condition (the cells are filled with air), III in a humid condition (the cells are filled up with water).

fig. I shows in the center the 4 right-angled central cells (C), surrounded by the 8 ring cells (R) and the 32 wing-cells (W). In fig. II and III the cells of the trichome are stipped: D the cover cell (=Deckzelle), A the water absorption cells, F the foot cell. The hatched cells are the epidermis cells (Ep) of the leaf surface.

fig. 10-15Trichomes of some representatives of the subfamily of the Pitcairnioideae:
fig. 10Pitcairnia atrorubens (C. KOCH) BAK.
fig. 11Fosterella penduliflora (C. H. WRIGHT) L. B. SMITH
fig. 12Hechtia (=Bakeria) tillandsioides (ANDRE) L. B. SMITH
fig. 13Abromeitiella brevifolia (GRISB.) CAST.
fig. 14Deuterocohnia longipetala (BAK.) MEZ
fig. 15Puya echinotricha ANDRE, centre of a trichome
fig. 16astellate trichomes of the inflorescence-scape of Puya ferruginea (RUIZ et PAV.) L. B. SMITH
fig. 16bsingle trichome enlarged. One cell is broken off.
fig. 17-27Trichome of some representatives of the subfamily of Bromelioideae:
fig. 17Orthophytum fosterianum L. B. SMITH
fig. 18Araeococcus flagellifolius HARMS
fig. 19Hohenbergia augusta (YELL) MORR.
fig. 20Streptocalyx longifolius (RUDGE) BAK.
fig. 21Bromelia balansae MEZ
fig. 22Aechmea aquilega (SALISB.) MEZ
fig. 23Cryptanthus racinae L. B. SMITH
fig. 24Wittrockia superba LINDM.
fig. 25Neoregelia spectabilis L. B. SMITH
fig. 26Nidularium innocentii LEM. var. innocentii
fig. 27Aechmea chantinii (CARR.) BAK.
fig. 28-32Trichomes of some representatives of the subfamily of the Tillandsioideae:
fig. 28Catopsis floribunda L. B. SMITH
fig. 29Guzmania insignis MEZ
fig. 30Tillandsia hildae RAUH
fig. 31Tillandsia usneoides L.
fig. 32aTillandsia rauhii L. B. SMITH. The trichome is embedded in a wax-layer.
fig. 32bTillandsia rauhii, 3 trichomes connected by water transportation channels.
fig. 33some types of Tillandsioideae-trichomes with regular cell sequences of the "cap" (=shield).
All plant photographs taken by Werner Rauh; all Stereoscan photographs taken by Rainer Schill, Nesta Ehler and Wilhelm Barthlott.



On our tree here at the Brooklyn Botanic Garden we have growing attached to each other by a stout rhizome two rosettes of Aechmea blumenavii, one of which is normal but the other one is not. The normal one has leaves about six inches long, in number, 15. A little up from the base the leaves when flattened out are about an inch and a half wide. The abnormal rosette consists of a cluster of outer leaves which is the rosette proper, and an inner cluster of smaller leaves that are somewhat different in size, getting shorter and smaller in a series of spirals toward the center. The inner leaves have a broad blackish line running longitudinally down the center, while the outer rosette leaves are plain green. The outer rosette leaves are narrower and longer than those of its companion normal rosette, being about an inch wide, and numbering again about 15. The inner leaves of this abnormal rosette number about 27. The difference in size of the smallest leaves of the outer rosette and the largest of the inner set is not sharp, there being a rather gradual loss of size as progression goes inward.

Here we have a freak, but one that seems to have a logical explanation . . . . . Many observations and studies by botanists have shown that the four units, or rings, of a flower—the sepals (the outer ring), the petals, the stamens (the pollen makers) and the ovary (the vessel that contains the "eggs" that are to become the seeds) are modified leaves. Of course, this is not obvious, resting on accumulated bits of information, but in the case of bracts, it can be observed often that they are modified leaves grown smaller. Bracts invest individual flowers and clusters of flowers, but in tall inflorescences arise from the lower part of the flower stalk and ascend into the main body of the flowers. The showy bracts of billbergias grow along the lower stem and up it to below the lower flowers. As pointed out above, they are leaves that have become specialized as to texture, size and color, but still have leaf shapes.

Sepals are most nearly leaf-like, and petals differ in color and texture from leaves, but the stamens and ovary have each become so highly specialized as to be unrecognizable because of the great modification of form. It thus develops that as one goes inward to the heart of the flower, the leaf-modification becomes more complicated. To look at it another way, involvement of flower structure proceeds inward leading to the seed, which is the means of progressive perpetuation, the goal of the life cycle. As far as the plant species is concerned, its most precious product is tucked away in a secret place where it is most protected until ready for its functioning.

Billbergia flower dissected to show parts. The single pistil consists of ovary, style and brush-like tip, the stigma.

In our abnormal rosette, a cogent character in this phenomenon is the stripe down the center of the inner leaves, adding more character and color to those leaves, a small step toward color and pattern in flowers, but a step, just the same . . . . It may be that the inner leaves represent bracts, and that no floral parts were initiated.

One hears people speak about reversions and throw-backs, but in this case I feel confident that this case does not represent anything this particular species underwent in its evolution. It is simply that the chemicals which "read out" and perform successive tasks in reaction or response to the unfolding of the life-history inherent in the chromosomes, became halted in the early stages of development through some disorganization, resulting in an erratic manifestation.

It is over a year ago that we used the flower-inducing chemical BOH (produced in Holland) on a number of our plants, and it is an afterthought after completing this article that the abnormal rosette could very well have been so treated. As I remember the plant and making the treatments, this could very well be.

—Brooklyn, New York.



Won't someone write a paper on the reason bromeliads don't always have perfect leaves. I am satisfied with the way mine look most of the time and am generally proud of them but sometimes when they seem at their best they begin to deteriorate. I know that sun can damage many and that after a plant blossoms it begins to die, but when you find a place that seems suitable, why does a plant gradually or suddenly develop changes that make it less than a show plant?

One of the most distressing things to happen is for the new leaves, as they first emerge, to develop gray, dry edges. I have a Vriesea fenestralis which for over a year was a beautiful plant, and which continues to thrive except that now a narrow band at the end of every new leaf is dry and gray. It grows side by side with V. hieroglyphica and V. gigantea that are beautiful plants and which have received identical care. Repeated rinsing of the cup, the use of rain water, root feeding, or withholding feeding are of no avail. No insecticide, fertilizer, or other material has ever been applied to the leaves or placed in the cup. The only other plant in my collection to have been so affected is Wittrockia superba.

Scale, both the small, hard black fly-speck scale that seems to be more or less limited to bromeliads, and the larger, brown scale that is common on many Florida plants are a major problem. The statement is found repeatedly that scale on bromeliads can be easily controlled with Malathion, while in literature related to other plants you are told it is effective only when scale is in the active crawling stage invisible to the naked eye, and not on scale in the non-crawling stage. You are also told Malathion must be rinsed out of the cup, but what do you do when the planting is in the ground or in trees out-of-doors or even in indoor "bromeliad trees" which can't be turned upside down?

Bromeliads very in their susceptibility to scale and perhaps one should only grow those that seldom are affected. In my experience the most highly susceptible is the ubiquitous Billbergia pyramidalis which I could do without, but almost as bad is Aechmea fasciata which I would hate to have to eliminate. So what do you do to prevent continued infestation?

What makes the edges of the lower parts of the leaves where they overlap one another become brown and papery? This, too, depends to some degree on variety, with vriesias seemingly the most often affected, but occasionally it happens even to the tried and true Neoregelia spectabilis and N. marmorata.

What makes the tips of occasional older leaves turn brown! What makes the small brown spots scattered over the leaves? The larger brown spots that turn white, become transparent and finally break through, which occur especially near the point where the leaf leaves the main part of the plant I have found to be infectious, but what infection, and how controlled? Two Hohenbergia stellatas from different sources that were introduced into my collection simultaneously both had a few such spots. They became rapidly worse, the leaves broke off near the base, and several plants in their immediate vicinity developed similar areas. These included especially A. 'Foster's favorite' and A. weilbachii. I isolated the affected plants, and no more seem to have been hurt.

What is meant when it is said that a plant is "hard to grow"? I assume it means you must have controlled humidity—but what humidity—proper temperature—but what temperature—proper soil and drainage and watering and light? Under what conditions would you expect Vriesea splendens or Guzmania musaica to thrive, or Wittrockia superba?

Here in south Florida we have high humidity and a fairly even temperature. I grow most of my bromeliads in a screened open area in which a plant can be given any amount of sun or shade. The older trees in the garden are full of naturally occurring tillandsias. Dyckias and bromeliads thrive in the cactus garden. A. 'Foster's favorite', N. marmorata, B. pyramidalis and others grow without attention in the ground, on the trunks of palms and on old logs. It would seem as if I should have only perfect plants among those I give the most care. Can someone help me attain this end?

—Fort Myers, Florida.



The bromeliad genus Tillandsia is so popular with collectors that one wonders how long the plants will last in their native habitat if collecting continues at the present rate. Tillandsia is well known for the extreme difficulty encountered in attempting to propagate it from seed.

In the July-August issue of the Journal Of The Bromeliad Society, Kelsey Williams reported his efforts in the green pod (embryo) culture of tillandsia seed by aseptic methods. He concentrated his efforts on green pod culture because in attempting to sterilize mature seed a foamy mess resulted. After reading about this, I mixed some tillandsia seeds with some sterilizing solution, shook them up, and noted no such foaming. I then decided to work on a method for the aseptic culture of mature tillandsia seed. It should be noted here that a few people have been successful in growing tillandsia seed by conventional methods and work in this direction should be continued.

In the following experiments seed of T. caput-medusae, T. xerographica, and T. schreiteri were used. Some seeds were sterilized in a 3% clorox solution and others in a saturated calcium hypochlorite solution. They were then transferred to an agar medium in 500 cc flasks. A few days later all flasks showed fungal contamination. Another problem encountered was that the long hairs of the seed wound around each other resulting in thick matted blobs of seed. In an attempt to overcome this, the seed was sown only a few at a time. This time large test tubes were used instead of flasks. 5% clorox and 10% clorox with a little detergent added was used to sterilize the seed this time. Exposure to the solution for 10 minutes resulted in no contamination, with germination of those seeds exposed to the 10% clorox being equal to those exposed to the 5% clorox. For germination of a few seeds this method works fine, but it is somewhat impractical for larger batches. After trying several methods, the following was found to work the best for growing larger numbers of seed. The medium is put in a laboratory petri dish instead of test tubes. The seeds are sparsely placed on top of the medium and then covered with a 10% clorox solution for 10 minutes. The clorox solution is then removed by submerging the bottom of a beaker with a slightly smaller diameter than that of the petri dish into the solution. This displaces some of the solution and when brought to rest on the seeds, holds them on the medium as the remaining clorox is poured off. The seeds are then washed with sterile water which is removed in the same manner as the clorox was. This technique takes very little practice to master and is not nearly so complicated as it sounds. It results in an even, untangled distribution of seeds. They now require no attention, except for the occasional addition of water to the medium if it should happen to start drying out, until they are ready to be transferred.

As for the medium used, both Knudson's C and Hill's formula were used. Those grown on Hill's formula are growing about twice as fast as those on the Knudson's C formula. Using this method you give the seedlings a good supply of water and nutrients, without the problem of fungal attacks. Some of the larger seedlings have grown to eight mm in six weeks.

—North Hollywood, California.

QUESTION: On my Aechmea weilbachii var. leodiensis and on my Nidularium × 'Francois Spae' the base leaves stay in their natural color, but some of the leaves in the second and third row turn brown while the rest of the foliage looks good and healthy. What causes the browning?

ANSWER: This is a most difficult question to answer, especially without any knowledge of the cultural conditions. Something is damaging the tissues of the plant at the base of the leaves, making it impossible for the leaves to pick up the necessary nutrients to sustain themselves. Consequently they just die off. Some things which might cause this condition could be a severe shock in temperature change, too much fertilizer, water with a high salt content, not enough water around the root system, or too much water during the cold winter months. Why haven't all the leaves been affected? Plants might be compared to people. If one gets the gout it affects the big toe first and spreads from there. So it is very likely that the crown of these plants will eventually rot out down to the base of the leaves that are damaged.


It is with deep sorrow that we have to announce the deaths of three good friends of our Society.

Ladislaus Cutak, of the Missouri Botanic Garden, passed away this January after an illness of a year. He had been a member of the Society from its inception and served on the Board for a number of years. A bromeliad and cactus enthusiast, he did much to further the popularity of these plants. All who knew Lad will miss his kindly, genial personality.

Beryl N. Allen was the mother of the Bromeliad Round Robin. Despite her 80 years and her 10 children, she was active in the plant world and was a great bromeliad fan. It was due to her indefatigable efforts that the Round Robin flew to all parts of the world. Her death will leave a void in the lives of her many friends.

Tom MacDougall was a dedicated plantsman and explorer who resided in Mexico. For more than 30 years he had studied the flora of southern Mexico and discovered a number of fine tillandsias. See the May-June, 1971 issue of the Journal for a picture of T. macdougalli and the last article that "Don Tomas" wrote for the Society. He passed away in January.

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