Morphological and Anatomical Studies in Helobiae

MORPHOLOGICAL AND ANATOMICAL STUDIES IN HELOBIAE

VII. Vascular Anatomy of the Flower of Butomus umbellatus Linn.* BY V. SINGH (School of Plant Morphology, Meerut College, Meerut) Received August 4, 1965

(Communicated by Prof. V. Purl, F.A.Sc.)

ABSTRACT The vascular anatomy of the flower of Butomus umbellatus--a member of the Butomaceae--has been described. The perianth and stamens remain fused with the gynoecium up to the level of the locules and thus showing a tendency towards epigymy. The six carpels are also adnate among themselves at the base for some distance. The vascular supply of a carpel consists of a dorsal bundle and two ventral bundles. The latter ramify repeatedly and the branches are distributed on the lateral walls of the carpel. The placentation in Butomus has been described as 'superficial' since the ovules are distributed almost throughout the inner carpel wall except the dorsal suture. It is considered that in cases like Butornus where carpels are free, the superficial placentation might have originated from marginal placentation by the unequal extension of the ventral surface of the carpellary margins. The present study also brings out certain resemblances in between Butomaceae and Hydrocharitaceae, while on the other hand vasculature of the flower hardly shows any resemblance to that of Alismaceae

THE vascular anatomy of the flower of some species of Potamogetonaceae, Najadaceae, Aponogetonaceae, Scheuchzeriaceae and Alismaceae has already been worked out by the author (Singh, 1965, a, b, c, d, 1966). The present paper deals with the vascular anatomy of the flower of Butomus umbellatus--a member of the Butomaceae, F.A.A. fixed material of which was obtained through the courtesy of the Director, National Botanic Gardens, Lucknow, India, and Professor Ernst C. Abbe, Minnesota, U.S.A.

* Research contribution No. 73 from the School of Plant Morphology, Meerut College, Metnart. 313 314 V. Sn,,lGx.i OBSERVATIONS The monotypic genus Butomus represented by B. umbellatus is distributed in temperate Asia and Eurasia. It is a freshwater slender emersed herb with a short rhizome and basal rosettes of erect, linear and triquetrous leaves. The scape is very long, erect and terete bearing numerous flowers on long slender pedicels in simple umbels. Before anthesis the inflorescence is enclosed by an involucre of three large, scarious bracts. The six subequal persistent perianth segments are petaloid and are arranged in two whorls of three each. The stamens are nine, free with flattened filaments and red- coloured, 2-celled, basifixed anthers opening by lateral slits. The six carpels are connate only at the base. The ovary of each carpel is unilocular with numerous, anatropous ovules scattered all over the inner surface of the carpel wall excepting the dorsal suture. The style is apical with the stigma on the inner side. The ripe carpels are free or nearly so and are crowned by persistent styles. The fruit is a many seeded inflated follicle. Anatomy of the Inflorescence and Flower.--The vascular supply of the peduncle consists of a large number of scattered collateral vascular bundles. Each bundle is surrounded by a bundle sheath of lignified cells. The sheath is more prominent especially in the outer region of the peripheral bundles. The phloem of the bundle is normal while the xylem is represented by a cavity associated with a few lignified elements. The outer seven or eight layers of the cortex are composed of small thin-walled rounded cells with diamond- shaped intercellular spaces while the inner cortex is very lacunaceous The epidermis is covered by a distinct layer of cuticle, and is beset by numerous stomata with small accessory cells. At the base of the umbel the vascular bundles of the peduncle branch and anastomose freely and then many traces diverge for each of the three involucral bracts. Thereafter many traces enter into the base of the pedicel of each flower and these soon organise almost into a ring of about 12 vascular bundles (Fig. 2). At the base of the receptacle the xylem cavity is completely replaced by lignified elements and the vascular bundles frequently split and anastomose to form a complete vascular cylinder (Figs. 3-5). Three traces for each of the six perianth segments diverge out from this vascular cylinder (Fig. 6). The traces for the outer whorl of perianth segments z_rise at a slightly lower level than those of the inner whorl. These traces may divide in their outward course through the cortex of the receptacle. The laterals further resulting in seven to nine bundles. The perianth lobes separate from the central part slightly above the level where the locules arc present (Fig. 12). Morphological and Anatomical Studies in Helobiae--.VI! 315 BUTOMUS UMBELLATUS

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• • J /-/II~L-~A( ))~%~-- 18 @4 5 t 15 FIGs• 1-18. Butomus tmtbellat.s. Fig. 1. Semi-diagrammatic longitudinal section of flower showing vaseular ground plan. Figs• 2-15. Serial cross-sections of flower-bud from base upward showing vascular supply to different organs. Fig. 16. A portion of longitudinal section of stigma showing glandular hairs• Fig. 17. Cross-section of an abnormal flower with ten stamens. One of the anther lobes of extra stamen is transformed into perianth segment (ps). Fig. 18. Cross- s-~ction of gynoecium with seven carpels from an abnormal flower. (d---dorsal bundle of carpel; psmperianth segment; st--staminal tra~; vs--ventral strand of carpel.) 316 V. SINGH

After the departure of the perianth traces, and before the gaps are completely filled up, nine traces diverge for the stamens almost simultaneously (Figs. 7, 8). Each stamen receives a single concentric vascular bundle which extends almost up to the top of the connective unbranched. The filaments separate from the central part simultaneously with the perianth. Two stamens lie opposite each perianth segment of the outer whorl and one each of the inner whorl. The vascular tissue left constitutes the gynoecium supply and gets re- organised into a more or less complete vascular cylinder. Six carpellary dorsals arise from this cylinder and take the midrib position in the six carpels (Figs. 9, 10). Then the vascular tissue breaks up into six V-shaped bundles arranged on radii alternating with those of carpellary dorsals (Fig. 10). These are the ventral strands of the carpels. Slightly above the level of the locules each of the two arms of a V-shaped ventral strand, which extends on either side of a locule, splits generally into five to seven bundles (Figs. 11, 12). The bundles thus derived from the two arms of a ventral strand lie on the lateral walls of the two adjacent carpels. These bundles give rise to traces for the numerous anatropous ovules scattered on most of the inner surface of the ovary walls of the carpels except the dorsal suture (Fig. 13). The cells present on the lateral sides of adjacent carpels are glandular and densely staining. They mark the limits of the two adjacent carpels. The separation of the carpels starts from the centre and extends towards the periphery (Fig. 13). The carpels remain coherent for about half of their length before they become completely free. Each free carpel is open on the adaxial side (Fig. 14) and the two arms are closely placed. The locule extends into the style and the style is also open on the adaxial side. The dorsal bundle as well as the ventrals after supplying the ovules continue into the style and the stigma (Figs. 1, 15). The stigma is covered by two to three celled glandular hairs arising from the cells of the internal lining (Fig. 16). The cells are densely staining and have distinct nuclei. Some variations in the number of stamens and of carpels have been observed. In one case there were ten stamens instead of nine. One of the anther lobes of the extra stamen was transformed into a perianth part (Fig. 17). Flowers with seven or eight carpels were also noticed. In such cases the vascular cylinder gives off corresponding number of dorsal bundles and ventral strands for the carpels. In one flower with seven carpels (Fig. 18), two of the carpels were fused throughout their length but their styles were free. There were two dorsal bundles in the fused carpels. Morphological atul Anatomical Studies bt Helobiae--Vll 317

DISCUSSION AND CONCLUSIONS In Butomus the perianth and the stamens remain fused with the gynoecium up to the level of the locules and thus showing a tendency towards epigyny. The six carpels are also adnate among themselves through the tissue of the floral axis at the base for some distance. Eber (1934) while studying the development of the gynoecium in Butomus described it as " Falsches Coenocarpes Gynaeceum" (Pseudosyncarpous gynoeeium). The side walls of carpels are glandular on their outer surface by whic'a the carpels become coherent at the base. Saunders (1929) compares these glandular surfaces with the septal glands of Liliaceae.

The vascular supply of a carpel consists of a dorsal bundle which extends into the stigma and two ventral bundles which branch several times. These branches are distributed on the lateral wall of the carpel. The profuse branching of the ventral bundles can be attributed to the fact that the ovules are distributed throughout the inner wall of the carpel except along the dorsal suture. The ventral bundles of the adjacent halves of two different carpels arise conjointly. Very recently Melville (1962) proposed a new theory of angiosperm carpel on the basis of the comparative morphology but he finds some support for it in anatomy. He suggested that the basic component of the ovary is a leaf with an epiphyllous fertile branch which together he calls ' gonophy!l ' From the fact that a placental strand supplies the two adjacent follicles of Butomus he concludes that the whorl of follicles originate from alternating whorl of sterile foliar organs (which he named as tegophylls) and a foliate dichotomously branched ovuliferous branch system. Thus, according to Melville (1962) the placentae are the independent structures developing from branch systems exillant to sterile leaves that form envelopes for the placentae. The gonophyll theory of the flower has received criticism at the hands of Comer (1963) and Puri (1963). According to Puri (1963) in cases like Butomus where each placental bundle ramify repeatedly the relation between the placenta and ovules cannot be explained by Melville. He rightly points out that~ "How can all the ovules, borne on the different ramifications that are believed to have become fused with the carpellary wall, have the same oriehtation ?" The carpels of Butomus umbellatus are interesting since their ventral edges are free and the ovules are distributed almost throughout the inner carpel wall except along the dorsal suture. Thus, they show resemblances 318 V. Sr~GH with some Ranales, particularly to Nymphaeaceae. As pointed out by Zimmermann (1930) when the entire or most of the internal surface of ovary wall is covered with ovules, as in the Nymphaeaceae and Butomaceae, the placentation should be described as "superficial" or "laminar" Regarding this condition Puri (1961, 1962) points out that the so-called "superficial" or "laminar" placentation is a unique problem in carpel morphology and the supporters of classical concept find it difficult to offer a suitable expla- nation of this phenomenon. He further adds that this fact does not lend any support to the conduplicate folding of the carpel. However, Puri (1962) suggests tentatively that "I have gazed at the condition in Butomus, Nymphaea, etc., quite a number of times without ever having a logical understanding of it in terms of the normal condition but this treatment of carpellary margins induces one to distinguish the ventral surface of the carpel into two categories. The carpellary margins and the rest of the lamina, while the former is potentially fertile and may bear ovules all along, the latter is sterile. If somehow the fertile ventral surface of the carpellary margins enlarges rather excessively and the rest of the ventral surface becomes suppressed except in the neighbourhood of the midrib, then a condition similar to superficial placentation will result". This view gets support from the condition seen in some species of Gentiana where the two halves of a parietal placenta separate apart due to the extension of the intervening regions of the carpellary margins and thus bring about the superficial placentation (see Gopal-Krishna and Puri, 1962). The present author is in complete agreement with the views expressed by Puri (1961, 1962). However, he is inclined to believe that in cases like Butomus where carpels are free the superficial placentation might have originated from marginal placentation by the unequal extension of the ventral surface of the carpellary margins. Most of the authors agree that Alismaceae and Butomaceae are closely allied families. Hooker (1894) and Rendle (1930) included the taxa of both the families under a single family Alismaceae. Johri (1936) on embryological grounds also supports a close affinity between the two families. Engler and Prantl (1889) placed the two families closely in the sub-order Butomoideae. Pichon (1946) suggested the transfer of all the members of Butomaceae, except Butomus to Alismaceae. However, Hutchinson (1959) placed Butomaceae along with Hydrocharitaceae under Butomales and Alismaceae in another order Alismatales. The present study ~lso brings out certain resemblances in between Butomaceae and Hydrocharitaceae. The ovary is completely inferior in Hydroeharitaceae, while Butomaceae shows a tendency towards Morphological w~d Anatomical Studies in Helobiae--VlI 319 epigyny. The vascular supply of the carpel of Butomus and Hydrocleis (Saunders, 1929) is very similar to that of certain members of the Hydro- charitaceae such as Hydrocharis. On the other hand, vascular anatomy of the flower hardly shows any resemblance to that of Alismaceae.

ACKNOWLEDGEMENTS

I am indebted to Dr. Y. S. Murty for his valuable guidance and keen interest and to Professor V. Puri for numerous valuable suggestions and critically going through the manuscript. My grateful thanks are also due to Professor Ernst C. Abbe, Minnesota, U.S.A., and the Director, National Botanic Gardens, Lucknow, India, for their generous help in sending the material.

REFERENCES

Corner, E. J. H. .. "A criticism of the gonophyll theory of the flower," Phyto- morphology, 1963, 13, 290-92. Eber, Von Etam .. "Karpallbau und plazentation sverh,~tltnisse in der Reihe der Helobiae," Flora, 1934, 127~ 273-330. Engler, A. and Prantl, K. Die ndtturliehen pflanzenfamilien, Wilhelm Engelman, Leipzig, 1889• Gopal-Krishna, G. and Purl, V. "Morphology of the flower of some Gentianaceae with special reference to placentation," Bot. Gaz•, 1962, 124, 42-57• Hooker, J. D. .. The Flora of British India, Vol. VI, Reeve and Co., London, 1894. liutchinson, J. •. The Families of the Flowering Plants, Vol. II, Second Edition, The Clarendon Press, Oxford, 1959. Johri, B. M. ... "The life-history of Butomopsis lanceolata Kunth," Proc. Ind. Acad. Sci., 1936, 4B, 139-62.

Melville, R. •. "A new theory of the angiosperm flower--I," Kew Bull., 1962, 16, 1-50. *Pichon, M. .• "Sur les Alimatac6es et les Butomac6es," Nat. Syst. ¢Paris), 1946, 12, 170-83.

Puri, V. .. "The classical concept of angiosperm carpel.--A reassess- ment," J. Indian bot. Soc., 1961, 40, 511-24. •. "On the concept of carpellary margins," Proc. S, mmer School Botany (1960), Darjeeling, 1962, pp. 326-33. •. "On the relation between ovule and carpel," J. Indian hot• Soe. (Maheshwari Commemoration Volume), 1963, 62 A, 189-98.

Rendle, A. B. .. The Classification of Flowering Plants, Vol. II, Second Edition, The University Press, Cambridge, 1930.

Saunders, Edith Rebecca .. "Carpel polymorphism-- HI", Ann. Bot., 1929, 43, 459-81. 32O V. ~N~.

Siajh, V. .. "Morphological and anatomical studies on Helobi~e. 1L Vascular anatomy of the flower of Potamogetonaceae,'" Bot. Gaz., 1965a, 126, 137-144. .. "Morphological and anatomical studies in Helobiae. IlL Vascular anatomy of the node and flower of Najadaceae,'* Proc. Ind. Acad. Sci., 1965 b, 61B, 98-108. .. "Morphological and anatomical studies in Helobiae. IV. Vegetative and floral anatomy of Aponogetonaceae," Ibid., 1965 c, 61 B, 147-59. .. "Morphological and anatomical studies in H¢lobiae. V. Vascular anatomy of the flower of Lilaea scilioides Buch. Ham.," Ibid., 1965 d, 61B, 316-25. .. "Morphological and anatomical studies in Helobiae. VL Vascular anatomy of the flower of Alismaceae," Proc. Nat. Acad. Sci., India, 1966 (In press). *Zimmermann, W. .. Die phylogenie der pflanzen, Jena, 1930.

* Not seen in originals.

30~66. Printed at The Bangalore Press, Mysore Road, Bansalore City, by K. V. Vm'adataba~ MmmSez, and Published by B. S. Ve-b~eh~,~ Editor, "Proceedings of the Indian Academy of Sciences," l~ngslore