A Preliminary Survey Based on the Sclereid Morphology

SYSTEMATICS OF MEMECYLON--A PRELIMINARY SURVEY BASED ON THE SCLEREID MORPHOLOGY

BY T. ANANDA RAO AND K. M. M. DAKSHNI* (Botanical Survey of India, 76, Lower Circular Road, Calcatta-14) Received March 23, 1963 (Communicated by Prof. L. Narayana Rao, y.A.sc.)

RESEARCrIES of Subramanyam and Rao (1949) and Rao (1947, 1951, 1957) have revealed that the presence of terminal foliar sclereids is an important generic character of Memecylon. On the basis of sclereid morphology, three major types are recognised. Filiform sclereids predominate in the majority of species. They are subdivided into separate sub-classes depend- ing on the nature of the branching and mature cell forms. Similarly, in those species exhibiting polymorphic sclereids the latter are segregated into distinct groups taking into consideration the main trends of variations. Thus the taxonomic interest of sclereid types as an aid in the identification of species of Memecylon and the utility of sclereid morphology in the problems of synonymy in the systematic treatment of Memecylon is examined by the study of a series of sterile or doubtful material obtained from Central National Herbarium (CNH) and Circle Herbaria of the Botanical Survey of India and an account of the results obtained is presented in this paper. I. Sclereid types as an aid in the distinction of species.NIn this attempt to utilise sclereids as an aid in the diagnosis of species, every care is taken to examine many leaves of the same sheet or from different sheets of the same species to recognise the range of variation. A number of doubtfully identified material revealed interesting features.

In two specimens (CNH 175356 and 175357) the leaves bear a remarkable resemblance to M. griffithianum Naud. but not in terete stems. However, the sclereids are filiform and of forking type as seen in M. griffithianum Naud. Hence it is identified as M. griffithianum Naud. Two sheets (CNH 175358 and 175359) bearing the same No. 117 collected by Bourdillon in Travancore agree with the description of M. laevigatum B1. Besides, sclereids are filiform

* Present address: Agra College, Asr~. 28 Systematics of Memecylon 29 and forking type as seen in M. laevigatum B1. It is of interest to record in this connection that this species is not reported in South India. The specimen No. 1269 (CNH 174727) collected by Bourdillon matches admirably with that of Wight's 1069 (CNH 174998) M. angustifolium Wt. Besides, sclereids are filiform and forking as seen in M. angustifolium Wt. In all the investigated species of M. amplexicaule Roxb. the sclereids are filiform and branching type (Rao, 1957). A number of specimens (CNH 174883, 174893-95) determined as M. amplexicaule Roxb. found to contain fruits of polyspermous character unlike the genus Memecylon. Besides, the cleared lamina of the above specimens clearly exhibited small gnarled polymorphic sclereids. In all probability the above sheets are incorrectly determined as M. amplexicaule Roxb. The field note described the epiphytic habit on other plants. Therefore the specimens belong to Plethiandra or Medinilla group and needs a critical comparison with the sheets of the above two genera. A doubtful specimen of Memecylon bearing the No. 39411 (CNH 175376 and 175377) collected by Ramaswamy in Kannikatty displays big leaf of 12-14 inches length and 3-3½ inches width, a cordate base and prominent nerves with punctations all over the surface of the lamina. The four wings under the nodes of leaves are not short but reach half way down each internode. On clearing the leaf, it was found to consist of filiform sclereids with a tendency to branch. The sclereid morphology and the description of the lamina agree with that of Memecylon amplexicaule Roxb. Hence it is concluded and indentified as M. amplexicaule Roxb. A further search for this material would be fruitful in view of the fact that this species is not recorded in the flora of Madras by Gamble. The specimen (Eastern Circle, B.S.I., Kanjilal 2073) from Sibasagar displays filiform non-branching sclereids. The plant is incorrectly determined as M. edule Roxb. var. cuneata CBC. because in M. edule var. cuneata or M. cuneatum Thw. sclereids are polymorphic idioblasts and vertically disposed in the form of I-girders touching the epidermal layers (Rao, 1957). Thus the sclereids of the above specimen closely approach the type found in Memecylon umbellatum Burm. (Syn. M. edule Roxb.) and in all probability it is incorrectly determined and included in the flora of Assam. The presence of terminal foliar sclereid is an important generic character of Memecylon. In one specimen No. 22703 collected by G.K. Dutta deposited in Eastern Circle of B.S.1. identified as Memecylon grande Retz. on clearing was found to contain no sclereids. Memecylon grande Retz, 30 T. ANANDARAO AND K. M. M. DAKSHN| has filiform terminal sclereids with a tendency to fork (Rao, 1957). Thus the specimen No. 22703 is in all probability a species of Eugenia rather than of Memecylon. In the specimens from Sibsagar (Kanjilal 4066, 2094) deposited in Eastern Circle of Botanical Survey of India the sclereids are comparable with that of M. scutellatum (Lour.) Naud. The sclereid morphology (Rao, 1957) has shown that M. edule Roxb. and M. elegans Kurz. have filiform sclereids whereas the specimens from Sibsagar (Kanjital 4066, 2094), identified as M. edule var. typica and M. elegans respectively, exhibit the type of sclereid as encountered in M. scutellatum (Lour.) Naud. The specimens are proposed and identified as M. scutellatum (Lour.) Naud.

When cleared the sclereids of specimen CNH 175285, were found to be fi!iform and branching whereas in M. myrsinoides B1. they are filiform of limited length (Rao, 1957). The features as seen in the above specimen are confirmed in nine separate collections identified as M. plebejum Kurz. In all probability it is correctly determined as M. plebejum Kurz. The sclereids of specimen No. 509 (CNH 175247) are filiform and non-branching whereas in M. heteropleurum B1. they are filiform and forking. I think it is correctly identified as M. kurzi King. The sclereids in sheet No. 452 (CNH 175325) are filiform and non-branching. The same feature is noticed in all the species identified as M. andamanicum Kurz (CNH 175322-175327). Thus the specimen No. 452 (CNH 175325) is M. andamanicum Kurz and not M. ovalifolium B1. where selereids of branching type are encountered (Rao, 1957). II. The utility of sclereid morphology in the problems of synonymy.- In one of the specimens of Memecylon (CNH 174695) collected by Thwaites bearing the collection number 2387 when cleared were found polymorphic sclereids as already described in Memecylon gardneri Thw. (CNH 174689, Rao, 1957). The specimen is treated under M. thwaitesii by Cogniaux but mixed up with M. gardneri "[hw. in the Flora of British India by Clarke (1879). From the standpoint of structure and topography of sclereids there is no difference between the specimens CNH 174595 and 174689. Thus the sclereid morphology supports that the two specimens are identical and M. thwaitesii Cogn. should be regarded as conspecific with M. gardneri Thw: The specimen 1No. 2~0 (C1NH 175292) collected by Heifer is identified as 3,1. obt~.stm ~all. In this specimen sclereids are short polymorphic type and can hardly be considered distinct from 3,1. scutellatum (Lour.) Naud. Systematics of Memecylon 31

The sclereid morphology supports Cogniaux's treatment of M. obtumus Wall. and M. edule Roxb. var. scutellata Triana. as M. scutellatum (Lour.) Naud.

In all probability there is confusion in the identification of M. anguxti- folium Wt. Wight's No. 1069 (CNH 174998)and Thwaites Nos. 1556 and 3346 (CNH 174994, CNH 174997) record sclereids of branching filiform type whereas in specimen No. 1031 (CNH 174995) identified as M. angustifolium and collected by Fisher in South India the sclereids are short and polymorphic type. The same feature was noticed in specimens Nos. 11716 and 15710 (CNH 175365 and 175366) collected by Gamble in South India of doubtful identification. The small idioblastic sclereids are sufficiently distinct from the filiform type of Wight's No. 1069. Certainly the above specimens do not match with the Wight's 1069. Specimen Nos. CNH 175364, 175365, 175366 exhibit short polymorphie sclereids of similar nature. They are identified as M. angustifolium var. helferi or M. helferi Cogn. A critical examination of Helfer's Kew distribution No. 2334 helps us in the identification of the above specimens. If Helfer's No. 2334 exhibit polymorphie sclereids then there is no doubt that M. angustifolium var. helferi is a good species as recognised by Cogniaux as M. helferi Cogn. rather,than a variety of M. angustifolium where sclereids are filiform and forking. In the writer's paper (Rao, 1957) M. angustifolium Wt. (Thwaites 1556) is erroneously cited as a species developing short fusiform sclereids. It is evident now that the above specimens exhibit filiform branching sclereids.

In one sheet of Thwaites 2468 (CNH 174932) two different plants are mixed up. One specimen marked (a) is correctly No. 1555 of Thwaites treated as M. heyneanum var. angustifolia by Clarke. Thus the specimen No. 1555 (a) of Thwaites (CNH 174932) exhibit sclereids which are short and polymorphic type whereas in M. heyneanum Benth. the sclereids are filiform with a rare tendency to branch (Subramanyam and Rao, 1949). The specimen marked (b) of Thwaites 2468 (CNH 174932) is distinctly different from Thwaites No. 1555 (a) and sclereids are filiform with a rare tendency to branch. The specimen is treated as M. heyneanum vat. latifolia or M. clarkeanum Cogn. Sclereid morphology supports its varietal status than a full-fledged species of Cogniaux as M. clarkeanum Cogn. In Thwaites 1555 (a) sclereids are short polymorphic. They are distinct idioblasts and in no way approach the sc/ereids as recorded in M. heyneanum Benth. The specimens is treated as a var. angustifolia by Clarke. This needs a critical study and stands a good chance to become an independent species. 32 T. ANANDA RAO AND K. M. M. DAKSHNI In the majority of specimens examined and identified as M. pauciflorum B1. the sclereids are of limited filiform non-forking type (CNH 174738). Miquel says (quoted by Clarke in FBI, 1879) that M. pauci[lorum B1. is hardly more than a form of M. myrsinoides B1. It has been shown (Rat, 1957) that sclereids are filiform and non-branching in M. myrsinoides B1. Sclereid morphology supports the view that M. pauciflorum B1. is conspecific with M. myrsinoides B1. However two sheets identified as M. pauciflorum B1. (CNH 174739, 174741) exhibit short polymorphic sclereids. They are distinct idioblasts and the specimens need critical study. In all specimens of Thwaites 2959 (CNH 174759-64, 174922) identified as M. varians var. rotundatum or M. rotundatum Cogn. the sclereids are short with a tendency to form ' Sclerocysts ' as seen in M. parvifolium Thw. (Rat, 1957). The sclereid morphology supports not much difference in M. rotunda- turn Cogn. and M. parvifolium Thw. In all probability Thwaites 2959 is M. parvifolium Thw. In the majority of specimens identified as M. edule vat. ramiflora CBC. the sclereids are filiform with or without a tendency to branch. However two sheets identified as M. edule var. ramiflora collected by Bourdillon (CNH 175159) at Travancore and also by Meebold (CNH 175118) at Travancore unlike the other sheets exhibit sclereids of short and polymorphic type. Wight's No. 1071 (CNH~175121)is not like M. edule vat. ramiflora. Besides sclereids are short and polymorphic and not like that of 1073 of Wight (CNH 175125) wherein the sclereids are filiform and forking. Sheets showing polymorphic sclereids resemble M. lustingtonii Gamble and needs critical examination of floral parts. Sclereids of Meebold specimen (CNH 175118) resemble that of 1071 of Wight (CNH 175121) not 1073 of Wight (CNH 175125). This sheet also resembles CNH 174739 (Thwaites 2959)which is treated as M. varians vat. B or M. rotundatum Cogn. However, sclereids in M. varians are filiform forking type. But in Thwaites 2959 (CNH 174759) sclereids are short and polymorphic with a tendency to cyst formation as seen in M. parvifolium BI. (Rat, 1957). It is of interest to recall Thwaites statement that his M. parvifolium is possibly a variety of M. varians. In view of its distinct idioblasts, it is either M. parvifolium B1. itself or distinct species M. rotundatum Cogn. as conceived by Cogniaux. Idioblasts are sutficiently distinct from each other to justify their maintenance at specific rank. In M. ellipticum Thw. sclereids are filiform and very rarely branching. The same feature was noticed in No. 3479 of Thwaites (CNH 174753, 174754). Systematlcs of Memecylon 33

This confirms Clarke's opinion that No. 3479 of Thwaites is M. ellipticum Thw. A sheet No. 5457 of Wray and Robinson (CNH 174800) seems to be incorrectly determined as M. maingayi CBC. It is seen (Rao, 1957) in several assemblage of leaves of M. maingayi (CNH 174799) sclereids are filiform and non-forking type, whereas in specimen No. 5457 sclereids are short steltate dendroid forms, a feature seen only in M. spthandra B1. In all probability the No. 5457 is art additional specimen near M. spthandra or M. spthandra itself.

M. pachyderrna Wall. No. 4104 of Wallich (CNH 174935) in all probability wrongly treated as conspecific of M. laevigatum B1. by Clarke. This specimen exhibits small polymorphic sclereids whereas in all the investigated specimens identified as M. laevigatum BI. (CNH 174937, 174938, 174939) the selereids are filiform and forking type. The distinct idioblasts of WaUich specimen cannot certainly be considered as modification of filiform type of sclereids. Sclereid morphology supports that M. pachyderma Wall. is an additional species and this cannot be conspecific of M. laevigatum. A sheet with the Col. No. 2686 of Thwaites (CNH 174694) differs from other examples of Thwaites 2686 (CNH 174691, 174692, 174693) in having perfectly round branches. However sclereids are filiform and non-branch- hag type in No. 2686 a feature seen in several leaves identified as M. macrophyllum Thw. (Rao, 1957). These features support Clarke's opinion that No. 2686 is M. macrophyllum Thw. Further, Clarke's view is that M. macrophyllum is not very much different from M. amplexicaule except the leaf size. But sclereids in M. amplexicuale are branching filiform type.

Thwaites No. 2998 (CNH 174767) is put with M. ovideum at Kew. Triana reduces the specimens identified as M. macrocarpum Thw. to M. ovideum. But according to Thwaites the one has a smooth calyx limb and the other a lamellate nerved one, besides there is a difference in petioles. Besides selereids are filiform, non-forking in No. 2998 while in M. ovideum it is often forked. It is very likely cerrect as Thwaites thinks that No. 2998 is M. macro- earpum Thw. than conspecific with M. ovideum~ A sheet bearing the No. 49 (CNH 175374, Old Branch) matches with Memecylon terminale Dalz. Sclereids are filiform and not forking. Clarke is of opinion that is probably not distinct from M. amabile Bedd. Sclereid morphology supports Gamble's view that M. arnabile as conspecific with M. terminale Dalz. B3 34 T. ANANDA RAO AND K. K. M. DAKSHNI

One sheet with the No. 149 of Herbarium Hookerianum 1867 (CNH 175307) collected by Vogel is identified as M. vogelii Naud. On clearing, the leaves were found to contain no sclereids. The species is treated by Cogniaux as synonymous with Spthandra memecyloides Benth. In view of the absence of sclereids, Cogniaux's attempt to reduce Spthandra memecyloides Benth. as syn. with M. vogelii needs critical study. Memecylon umbellatum Burro. (M. edule Roxb.) is a composite species and Indian forms need to be collected and studied. This species has been shown (Subramanyam and Rao, 1949; Rao, 1957) to exhibit the most variable type of sclereid morphology. Of the several varietal forms proposed by Clarke, number of different leaf collections have been cleared and analysed to see how far there is justificatior~ for reduction of Cogniaux's distinct species into number of varietal status. On the basis of sclereid morphology the several varieties can be arranged in two groups as follows: Group I includes M. cuneata Thw. (M. edule Roxb. var. cuneata CBC.) and M~ scutellatum (Lout.) Naud. (M. edule Roxb. vat. scutellata Triana). In these species the sclereids are distinct idioblasts (Rao, 1957)and in no way approach the type of filiform sclereids as exemplified in M. edule Roxb. The sclereids of the above two species are so peculiar that it would be difficult to conclude that one type is a modification or a trend of the sclereids found in M. edule. The sclereid morphology supports Cogniaux's treatment of M. edule Roxb. var. cuneata CBC. and M. edule Roxb. var. scutellata Triana, as M. cuneatum Thw. and M. scutellatum (Lour.) Naud. as two additional species. Group !I includes M. leucanthum Thw. (M. adule Roxb. var. leucantha CBC.), M. rubro-caeruleum Thw. (M. edule Roxb. var. rubro-caerulea CBC.), M. molestum Cogn. (M. edule Roxb. var. molesta CBC.), M. urceolatum Cogn., M. Capitellatum L. (M. edule Roxb. var. thwatiesii CBC.), M. capitellatum not of Linn. (M. edule Roxb. var. laeta CBC.), M. edule Roxb. var. ramiflora CBC. and M. edule Roxb. var. rottleriana CBC. In these species the filiform sclereids are greatly elongated but differ from one another in the extent of branch system. This feature supplemented by the histology of leaf and stem may be useful in elucidating the real status of varietal forms. M. grande Retz. is characterised by filiform sclereids, often exhibiting branch system. This feature is confirmed by examining four separate leaf collections (CNH 174811, 174813, 18927). Some of the sheets which are doubtfully determined as M. grande var. horsfieldii (CNH 174821) and M. grande Systematics of MemecyloJl 35 vat. khasyana (CNH 174824, 174825, 174820)are found to display filiform sclereids without any branch system. The sclereid morphology of the above variety corresponds to that of M. celastrinum Kurz. which has filiform non- branching sclereids (Rao, 1957). Thus from the standpoint of the structure and topography of foliar sclereids King is correct in grouping them under M. celastrinum Kurz.

SUMMARY

The taxonomic interest of sclereid types as an aid in the identifications of species of Memecylon and the utility of sclereid morphology in the problems of synonymy in the systematic treatment of Memecylon is considered in this paper.

ACKNOWLEDGEMENT

The authors wish to express their gratitude to Dr. M. A. Rau, the Regio- nal Botanist, for his encouragement in the preparation of this paper.

REFERENCES

Hooker, J.D., et aL .. The Flora of British India, 1879, 2, 553-64. 11~o, T. A. .. "Studies on foliar sclereids in dicotyledons. II. On sclereids in species of Leucospermum (Proteaceae), Mimu~ops (Sapo- taceae) and Memecylon (Melastomaceae)," J. Univ. Bombay, 1947, 19, 25-31. .. "Studies on foliar sclereids," J. Indian. hot. Soc., 1951,. 30, 28-39. .. "Comparative morphology and ontogeny of foliar selereids in seed plants. I. Memecylon L.", Phytomorphology, 1957, 7, 306-30. Subramanyam, K. and Rao, "Foliar sclereids in some species of Memecylon L.", Proc. T.A, Indian Acad. Sci., 1949, 30, 291-98.