THE FLORAL ANATOMY OF ELETTARIA CARDAMOMUM MATON, A RE-INVESTIGATION

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1 THE FLORAL ANATOMY OF ELETTARIA CARDAMOMUM MATON, A RE-INVESTIGATION BY R. M. PAI Department of Botany, Marathwada University, Aurangabad, India {Received 13 July 1964) SUMMARY The re-investigation indicates that the epigynous glands of the cardamom flower, as in other species of Zingiberaceae, are vascularized emergences of the ovary. Anatomical evidence has been adduced in support of the classical view that the labellum of the cardamom flower is a double structure. The observations of Thompson and Gregory, in this connection, are re-interpreted and it is shown that the mid-anterior strand in the labellum is a fusion product of the marginal traces of the two component members belonging to the inner androecial whorl. INTRODUCTION Recent anatomical studies (Rao, Karnik and Gupte, 1954; Rao and Pai, 1959, i960; Rao and Gupte, 1961) indicate that some of the conclusions arrived at by Gregory (1936) in the case of the cardamom flower are not in accordance with the facts. A re-investigation of the species was, therefore, undertaken and the results are presented in this paper. MATERIALS AND METHODS Material was collected from the cardamom plantations in Sirsi, North Kanara, Mysore State and fixed in formalin-acetic-alcohol. Serial transactions of paraffin infiltrated material were stained in crystal violet using erythrosin as a counter stain. RESULTS Two rings of bundles, each with six strands, run in the floral axis beneath the ovary (Fig. i). The inner ring contains three large strands and three small radially flattened bundles alternating with each other. The latter travel initially outwards (Fig. 2) and, thereafter, run an upward course opposite the loculi of the ovary (Figs. 4-7). Simultaneously, the bundles of the outer ring also travel out exhibiting extensive branching during their outward transit and subsequently traverse the ovary wall which thus contains numerous discrete strands, many of which are very small; in fact too small to be easily noticed (Figs. 4-6). The three large bundles of the inner ring which are the placento-parietal bundles extend laterally to form a temporary siphonostelic cylinder of vascular tissue (Fig. 3). A little higher, the three bundles separate out and divide into the outer parietal and inner placental strands (Fig. 4). The former run opposite the septa of the ovary in the ovary wall. The lower parts of the ovarian loculi bear no ovules (Fig. 5). The placental bundles, initially, merge to form a tri-radiate axile strand (Fig. 5). At 187

2 i88 R. M, PAI 10 Figs. I 12. Serial transections from the floral axis upwards through the flower of Elettaria caidanwtnum, C = median trace of a petal; G = gland; MS = median trace of a sepal; P = parietal bundle; St = staminal trace; V = vascular plexus. All figures >; 125.

3 Floral anatomy of Elettaria cardamomum 189 the beginning of the ovuliferous zone, the composite placental cord divides into a few strands, chiefly located at the inner ends of the septa (Fig. 6) which end in sending traces to the ovules. They bear no branches in the non-ovuliferous zone. The loculi persist as stemic cavities above the ovuliferous zone. They project inwards as narrow channels which become closed in such a way as to enclose three axile cavities (Fig. 7). At this level, many of the small strands in the ovary wall usually end leaving a 19 Figs Serial sections through the flower of Elettaria cardamomum continued from Figs. I-I2. F = filament; L = labellum; LSt = lateral staminode. All figures x 125. Figs ring of nine strands in groups of three each, the median bundles of every set being the small median bundle of a sepal (Fig. 7). The three axile cavities fuse to form a central tri-radiate canal, which is continued into the style. The parietal bundles increase in size, divide into two or three strands and bear outer and lateral branches, adjacent ones of which fuse to form an anastomosing vascular plexus on top of the ovary (Fig. 8). Some bundles of the outer ring may be associated with the plexus but the median traces of the

4 190 R. M. PAI sepals remain unaffected. From the anastomosing plexus is derived the vascular supply to the petals, the androecium, the glands and the style, A transverse section above the level of the plexus (Fig, 9) shows: (i) an outer ring of nine bundles representing the vascular supply of the cal5rx, (2) an inner ring of about fifteen to seventeen strands representing the vascular supply of the petals and the androecial members, (3) two prominent masses of vascular tissue in antero-lateral positions for the two epigynous glands, and (4) two traces flanking the arms of the V-shaped canal for the style. The glands and the style are the first to separate from the outer column of tissue above the ovary (Fig. 11). The calyx with the nine strands separates next from the inner floral tube. The glands are initially attached to the outer column of tissue for a short length but higher up lie freely within the floral tube. The two masses of vascular strands enter the two glands and, within them, extend in an antero-posterior direction. Nine of the fifteen to seventeen bundles at the base of the floral tube (Fig. 11) are arranged in groups of three each, one set posterior and the other two antero-lateral, corresponding in positions to the parietal bundles. These are, in fact, the daughter strands of the parietal bundles formed at the level of the plexus. Radially opposite the median bundle of the posterior set, is a prominent strand which originally constituted the original median strand of this group, but which moved out subsequently. It represents the median bundle of the posterior petal (Figs. 11 and 12). The present median strand of the posterior set is derived through a bifurcation of one of the original laterals. This set represents the main vascular supply of the stamen. The median strands of the two antero-lateral sets function as the median bundles of the two lateral petals. Higher up, the floral tube develops three ridges on its outer face, one posterior and the other two antero-lateral (Fig. 12). Some of the bundles in the floral tube, especially in the anterior and the antero-lateral positions, divide and some of them travel out into the ridges. The latter subsequently separate from an inner cylinder and represent the three petals (Fig. 13). The larger, posterior petal embraces the two other smaller, anterolaterals (Fig. 14). The inner cylinder represents the fused bases of the labellum, the lateral staminodes and the stamen. This cylinder splits into two segments, a flat posterior one and a thick, crescentic anterior one. From the margins of the posterior segment two small lobes, each with a single strand become separated (Fig. 15). These thin, vascularized lobes represent the reduced lateral staminodes. The flat median part of the segment is the filament which contains five strands one median, two laterals (which exhibit a double nature) and two small end traces which merge with the laterals to reduce the number of bundles in the connective to three (Fig. 16). In the upper part ofthe anther, the connective is very much reduced in width and appears as a narrow plate connecting the large anther lobes on either side (Fig, 17). The lateral strands also lose their double nature. The median strand splits into two and each of the resultant bundles travels towards the laterals. The connective itself, splits in the middle and separates from the anther a little later. The bundles in the connective run in the split crest of the anther and disappear (Fig. 18). The thick crescentic anterior segment is the base of the labellum. One of the bundles is on the mid-anterior line and opposite it the labellum develops a shallow groove on its inner face. This bundle divides higher up into two (Fig. 19), The daughter strands also shift laterally. In some flowers, a very early division of this strand is observed (Fig. 10), The labellum may, or may not, divide into two segments (Figs, 20 and 21), The style contains a V-shaped canal and two strands flanking the arms of the V (Figs, 11-16). In some flowers, in addition to these two, a third, 'blind', anterior strand appears

Floral anatomy of Elettaria cardamomum 191 in the style (Fig. 17). When the anterior strand is present, it is the first to disappear and then the other two (Fig. 18).

5 Floral anatomy of Elettaria cardamomum 191 in the style (Fig. 17). When the anterior strand is present, it is the first to disappear and then the other two (Fig. 18). DISCUSSION Some of the observations made by Gregory on the course of the vascular bundles in the cardamom flower appear curious and irreconcilable in the light of the present description of the fioral anatomy of the plant. Gregory describes the presence of twelve traces, nine peripherally disposed in groups of three each and three forming a central group in the pedicel. However, I find that the median traces of the peripheral three sets are actually derived from the inner of the two rings which initially, therefore, contains six traces. Their presence in the outer ring occurs only as a secondary feature. Evidently, Gregory based his description from sections taken a few microns beneath the ovarian loculi and not from lower levels. His account of the further course of these traces is noteworthy. It is best expressed in his own words. 'These three bundles of the peripheral group, after supplying bundles to the sepals on the same radius, proceed upwards; the laterals then terminate in a member of the outer staminal whorl, while the median one is continued into the same radial position of the style. The course is the same for the other two groups of peripheral bundles' (Gregory, 1936). In the present investigation, no such condition was observed. The median of the peripheral sets which run opposite the loculi represent, as pointed out in an earlier section, only the median traces of the sepals. The laterals, along with the parietal bundles, form an anastomosing plexus which is a very important anatomical development in the zingiberaceous fiower and has been universally observed in the species so far studied, but which Gregory somehow seems to have missed in his specimens of the cardamom flower. In the present study of the same plant, the laterals of the peripheral groups were observed to take part in the formation of the vascular anastomoses which contribute not merely the vascular supply to the glands (which Gregory regards as non-vascular) but the vascular supply to the corolla, the androecium and the style as well. Also, the marginal traces of the sepals are derived from these laterals. It is pertinent to note here that the medians of the peripheral groups run as the median bundles of the sepals, leaving no vascular tissue at all at the top of the ovary. The fact that these traces do not take part in the development of the plexus is also significant. Evidently, therefore, Gregory's observation that 'the median one is continued in the same radial position of the style' is not substantiated in the present study of the cardamom fiower. The median of the three daughter strands derived from the parietal bundles, above the vascular plexus, which are, in turn, derived from the inner ring of bundles of the pedicel, function as the median bundles of the petals. The parietal bundles themselves do not constitute that ring, for the original three bundles of the ring are a fusion product of the parietal and placental strands. The presence of vascular bundles in the axile region of the ovary is not mentioned in the earlier account. These have been observed in specimens studied here. Such vascular strands are also present in the zingiberaceous species studied so far and are referred to as the placental bundles concerned with the bearing of branches to the ovules. According to Gregory, ovular traces are borne by the three bundles running opposite the septa which constitute the inner of the two rings in the pedicel of the cardamom fiower. These are obviously the parietal strands in this zone. In no other species of Zingiberaceae studied do the parietal bundles send branches into the ovules. It may be pointed out here that the

6 192 R. M, PAI three bundles to which Gregory refers are compound cords, being the fusion product of the parietal and the placental strands. Just below the base of the ovarian loculi, these spht into the consituent strands the inner placental and the outer parietal bundles. It is the former which are concerned with bearing traces to the ovules and to which no reference is made nor even indicated in Gregory's (1936) Fig. 3-J, p Gregory regards the glands of Elettaria as simply epidermal appendages of the ovary, since, according to him, they do not contain any vascular tissue. Rao (1963) opined that this needed confirmation. In this re-investigation, the glands are found with very prominent masses of vascular tissue. In all the species of Zingiberaceae investigated, the glands are vascularized. The presence of vascular tissue seems to be connected with the more organized nature of the glands (cf. Fsau, 1953). Furthermore, it appears that the glands are not merely epidermal emergences of the ovary. Comparative observations on the variation in their form, structure, development and vasculature, seem to suggest strongly that they are more deeply connected with organs ofthe ovary (^cf. Pai, 1961). However, it must be conceded that Gregory is correct inasmuch as he associates the glands with the ovary and, at the same time, regards them as of no particular significance in morphological considerations of the zingiberaceous flower. The mid-anterior bundle in the floral tube is considered significant by Gregory in the consideration of the morphological nature ofthe labellum. It is derived from the plexus. It shows an early division into two strands in a few flowers studied here (Fig. 10), and Gregory admits this fact (1936, Fig. 3-O to ZZ, p. 366). In other flowers ofthe same plant, it continues for a considerable length in the floral tube and in the labellum (Figs. 9-16). On the basis of the 'structural isolation of the central group of bundles in the labellum from the lateral ones', it is assumed that the labellum is a triple structure. The connection of the mid-anterior bundle with the others that enter the labellum is deeper than was realized by Gregory. Moreover, he has observed only the venation of the labellum and that under a dissecting lens. That the central group of bundles is isolated cannot be maintained as well, since the bundles show repeated inter-connections and branchings with the adjacent bundles in the labellum. Moreover, in their derivation they do not show such a significant deviation from that of the other bundles of the floral tube as to warrant their recognition as a separate, or distinct, entity. There is reason to believe that the development of the mid-anterior trace in the labellum is a secondary feature. The evidence obtained in the present study may very well be adduced in support of the classical conception (Payer, 1857; van Tieghem, 1868, 1871), that the labellum is double rather than triple. This mid-anterior strand may conveniently be interpreted as a composite bundle being the fusion product of the marginal bundles of the two component members of the inner androecial whorl. The variation seen in the course of this strand in some of the plants studied bears testimony to this contention. In Zingiber macrostachyicm Dalz. (Rao and Pai, 1959), there is, right from the beginning, no mid-anterior strand but, laterally on either side of the mid-anterior line, the marginal bundles ofthe two constituents are present (Fig. 50, Rao and Pai, 1959) and they continue upwards into the two segments of the labellum. The same condition occurs in some other species also, e.g. Curcuma decipiens Dalz. (Pai, 1962). In Kaempferia scaposa Benth. (Rao and Pai, 1959, Fig. 18), Curcuma amada (Pai, 1962), etc., it is present for a short length and quickly divides into two. The resultant traces also continue for the rest of the length of the labellum and into the two segments. In Globa bulbifera Roxb. (Pai, 1963)' the labellum itself consists of two segments which marginally merge feebly for a short

Floral anatomy of Elettaria cardamomum 193 length to form the composite structure the labellum. Later, it splits up once again into its constituents.

7 Floral anatomy of Elettaria cardamomum 193 length to form the composite structure the labellum. Later, it splits up once again into its constituents. There is also no development of a median bundle in the lahellum. The condition in other species studied falls into one or the other of the above mentioned types. In my opinion, the development of a mid-anterior strand and its further behaviour are related to variations in the forces at work connected with the union of the two component members of the labellum. Gregory claims support from external morphology for his contention that the labellum is triple in constitution. He finds it more or less three-lobed which he considers significant from the point of view of its morphological nature. In specimens studied here, certain flowers show a median apical split whereas others do not. In the latter type, the form of the labellum is similar to that figured by Gregory. In cases where the labellum is emarginate, it is marked by an early division of the median strand and the bundles run into the two components. When the apical notch is absent, the median strand in the labellum continues for some length and then clearly exhibits a bifurcation which Gregory has also observed. This might once again be taken in support of the contention that the development of the mid-anterior bundle in the labellum is related to the degree of connation of its two components. Although connation has progressed in some flowers removing all external indications of the constitution of the labellum, vascular anatomy helps us to understand its morphological nature. In this connection, the remarks of Willis (1948), seem signiflcant. According to him, the labellum in Zingiberaceae might be t\vo- or three-lobed but it still comprises only the two antero-lateral members of the inner androecial whorl. The evidence of Thompson (1933, 1936), may well be construed to accord with the classical conception. That primordium 8 is small would imply that the labellum is constituted chiefly of emergences 11 and 13 belonging to the inner of the two androecial whorls, the posterior members of which is the functional stamen corresponding in position with primordium 12. It appears very likely that primordium 8 is not elaborated beyond the primordium stage at all and may conveniently be taken as of no account in morphological considerations. This is perfectly in agreement with the classical view which holds that the dorsal stamen in the family is suppressed and primordium 8 corresponds with this stamen. Thus, in the opinion of the present writer, the labellum in Elettaria, or, for that matter, in most of the Zingiberaceae seems best interpreted as a double structure. The classical view is too strong to be seriously challenged, much less refuted, and the ontogenetical and anatomical evidence provided by Thompson and Gregory, if accurately appraised, may still be aligned in support of this view. ACKNOWLED GMENTS The writer expresses his grateful thanks to Professors (Mrs.) Ella Gonzalves, V. S. Rao and V. R. Dnyansagar for their stimulating help and interest. REFERENCES ESAU, K. (1953). Plant Anatomy. New York. GREGORY, P. J. (1936). The floral morphology and cytology of Elettaria cardamomum Maton. J. Linn. Soc. (Bot.), 50, 363. PAI, R. M. (1961). On the floral morphology of Curcuma longa L. Curr. Sci., 30, 274. PAI, R. M. (1962). Studies in the vascular anatomy of the flower in the Scitamineae and the Burmanniaceae. Ph.D. thesis, Bombay University. PAI, R. M. (1963). On the morphology of the labellum of Globba bulbifera Roxb. Vidarbha J. Sci., i, 19. PAYER, J. B. (1857). Traite d'organogenie Comparee de la Fleur. Paris. B NP

8 194 R. M. PAI RAO, V. S. (1963). The epigynous glands of Zingiberaceae. New PhytoL, 62, 342. RAO, V. S. & GUPTE, K. (1961). The floral anatomy of some Scitamineae. IV. ^. Univ. Bombay, B, 29, 134, RAO, V. S., KARNIK, H. & GUPTE, K. (1954). The floral anatomy of some Scitamineae. I. J. Indian bot. Soc, 33, 118. RAO, V. S. & PAI, R. M. (1959). The floral anatomy of some Scitamineae. II. J. Univ. Bombay, B, 28, 82. RAO, V. S. & PAI, R. M. (i960). The floral anatomy of some Scitamineae. III. 7- Univ, Bombay, B, 28, i. THOMPSON, J. McL. (1933). Studies in advancing sterility. VI. The theory of scitaminean flowering. Publ, Hartley Bot. Lab. {Liverpool), 11, THOMPSON, J. McL. (1936). On the floral morphology of Elettaria cardamomum Maton. Publ, Hartley Bot, Lab, (Liverpool), 14, TIEGHEM, VAN P. (1868). Recherches sur la structure du pistil. Annls Sci, nat,, Bot,, 12, 127, TIEGHEM, VAN P. (1871). Recherches sur la structure du pistil et sur l'anatomie compar^e de la fleur, Mem. Savants etrangers a I'Institut, II, 21, i. WILLIS, J. C. (1948). A Dictionary of Flowering Plants and Ferns, Cambridge University Press.

THE EPIGYNOUS GLANDS OF ZINGIBERACEAE

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