ON A PETRIFIED PALM PETIOLE FROM MOHGAON KALAN AREA,

Miss VIMALA K. MENON (Department of Botany, University of Lucknow) Received November 16, 1964 (Communicated by Prof. L. Narayana Rao, F.A.SC.)

INTRODUCTION

THE present paper deals with a piece of petrified palm wood, measuring 13 cm. long and 3.2 cm. broad, collected from Mohgaon Kalan area of the Deccan Intertrappean series. The fact that the cortical part is recognisable shows that it could not have been very much bigger than what it is. This leads one to the inference that it may probably be the distal part of a petiole or rachis or inflorescence axis rather than a stem.

DESCRIPTION The specimen Maz is black in colour and seems to have become flattened and slightly damaged during preservation (Photo 1).

ANATOMY Transverse sections of the specimen show two regions--the cortical and middle, the latter divisible into two parts, the peripheral and central, on account of the variation in the bundle forms. Due to crushing during fossilization little bits have become separated from the rest of the wood as shown by an arrow in Photo 2. In the cortical region the fibrous bundles are in two rows, the smaller ones are on the peripheral side and the bigger ones are on the inner side (Text-Fig. 1). Below the fibrous bundles are seen regularly distributed bigger and smaller fibrovascular bundles (Photo 3, Text-Fig. 1). Frequency of the bundles per cm. 2 at different zones could not be made out as the specimen itself is very small in circumference. A typical fibrovascular bundle consists of dorsal and ventral sclerenchymatous sheaths, of which the ventral is generally bigger and is separated from the dorsal by parenchyma (Text-Figs. 2 and 3). The ventrally placed xylem element is confined to ~ 17 18 MISS V~MALAK. MENON

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5 16 17- 1 T~xT'-Ftcs. 1-23. Fig. 1. Distribution of fibrovascular bundles in the cortical region, x 32. Figs. 2 and 3. Different types of fibrovascular bundles from the cortical region ×60. Fig. 4. Distribution of fibrovascutar bundles in the peripheral part, ~:32. Figs. 5 and 6. Different types of fibrovascular bundles from the peripheral part, w60. Fig. 7. Distribution of fibrovascular bundles in the central part. ;< 32. Figs. 8--16. Different types of fibrovascular bundles from the central part, ,..60. Figs. 17-19. Diminutive bundles from the central part, ×60. Figs. 20 and 21. Lobed bundles of the central part, x 60. Fig. 22. A portion of the ground parencbyma in transverse seciton, x 60. Fig. 23. A small portion of ground parenchyma with wavy margins, x 60. db, diminutive bundle ; dsc, dorsal sclerenchyma : fb, fibrous bundles ; fvb, fibrovascular bundle ;. Ib, lobed bundle; ph, phloem; rsc, ventral sclerenchyma; xy, xylem. Petrified Palm Petiole from Mohgaon Kalan Area, Madhya Pradesh 19 only one. Phloem is not preserved though dorsal in position. The f/v ratio of the bundles is 0.8/1 to 1-4/1 and their diameter is 0.28 to 0.5 ram. Stegmata and radiating or tabular parenchyma round the bundles are not clear. Peripheral part of the middle region consists of regularly distributed two to three rows of vascular bundles which are smaller than the cortical bundles (Photo 4, Text-Fig. 4). The amount of dorsal sclerenchyma in these oval or round bundles (Photo 5, Text-Figs. 5 and 6) is lesser than in the cortical bundles. The ventral sclerenchyma covers more than 3/4 of the xylem element, is many times bigger than that of the dorsal sheath and is separated from it by the ground parenchyma cells. The xylem is reduced to only one element which is mostly rounded or sometimes oval. Phloem is not preserved. The f/v ratio of the bundles is 0.8/1 to 1.7/1 and their diameter is 0.19 to 0.31 mm. Diminutive bundles are seen in between the normal bundles (Text-Fig. 4). Fibrous bundles, stegmata, tabular and radiating parenchyma are absent. In the central part of the middle region the tissues are slightly compressed and crushed so that it gives the impression that the fibrovascular bundles are closely placed (Photo 6, Text-Fig. 7). In the bundles the dorsal and ventral sclerenchyma join together and form a complete sheath round the vascular elements (Text-Figs. 8 to 16). Separate sheaths are very rarely seen in this part. The bundles are mostly rounded to oval in shape (Text-Figs. 8 to 16). The centrally placed xylem element is generally one (Text-Figs. 7 and 8)but occasionally more than one (Text-Figs. 9 to 12) or even elongated due to lateral compression (Text-Figs. 13 and 14). The phloem is seen only in some bundles, but cannot be located in those bundles where a centrally placed solitary xylem is surrounded by a uniform sclerenchymatous sheath (Text-Figs. 13 to 16). Generally in the bundles although the sheath is complete, yet the ventral part is thicker than the dorsal (Text-Figs. 8 to 12). Diminutive bundles (Text-Figs. 7 and 17 to 19) are scattered between the bigger ones. Fused bundles also occur in this region (Text~Figs. 20 and 21). Fibrous bundles, stegmata, radiating or tabular parenchyma are absent. The ground tissue better preserved in the middle part than the cortical, is compact and consists of smaller thin-walled and angular cells (Text- Fig. 22). But at some places these cells are seen with wavy margins (Text- Fig. 23). Longitudinal sections of the specimen show scalariform pitting of the xylem elements (Photo 7), 20 Miss VIMALA K. MENON

TABLE I

Characters Palmoxylon mahabalei Mz.,, Palmocaulon raoi

Cortex Present Present .. /Fibroes Present, 2 rows Present, 2 rows .. bundles Fibrovascular Regular, Bigger in Regular, Bigger in bundles s~ze s~ze .. Sclerenchyma Both dorsal and Both the sclerenchyma in vascular ventral well-deve- sheaths well deve- .. bundles loped sclerenchyma loped Xylem vessels One to two Mostly one .. F/v ratio 0.7/1-1.8/1 0.4/1-1.4/1 .. Diameter 0.15-0- 93 mm. 0.28-0- 5 mm. .. Peripheral part Present Present Present Fibrovascular Regular, wide in dis- Regular, wide in dis- Regular, close in dis- bundles tribution tribution tribution Sclerenchyma Dorsal sheath small, Smaller dorsal sheath Complete sheath of of vascular while the ventral and very much sclerenchyma in bundles shgath is many bigger ventral which ventral side is times bigger than sheath bigger than dorsal dorsal side Xylem vessels Mostly one Usually one Many arranged in a crescentic manner F/v ratio 0.76/1-3.1/1 0.8/1-1.7/1 1.5/1-4.7/1 Diameter 0.23-0.72 mm. 0.19-0.31 mm. 0'29-0.91 mm. Fibrous Absent Absent Absent bundles Central part Irregular, close in Irregular, slightly Irregular, wide in dis- distribution close in distribution tribution Sclerenchyma Dorsal sclerenchyma Complete sheath of Complete sheath of of the fibro- very much smaller sclerenchyma sur- sclerenchyma with a vascular than ventral scleren- rounding the vascu- very much smaller bundles chyma. Some- lar elements dorsal side than times both joined ventral side together Xylem vessels One One Many, crescentic arrangement Petrified Pahn Petiole from Mohgaon Kalan Area, Madhya Pradesh 21 TABI~E I (Contd.)

Characters Palmoxylonmahabalei Ms2 Palmocaulonraoi

F/v ratio 0. 6/1-2. 9/1 Could not be 0.68/I-1.6/1 measured Diameter 0.23-0"8 mm. 0.13-0.3 mm. 0.23-0.69 ram. Fibrous Absent Absent Absent bundles Ground tissue Compact, rounded, Compact, thin-walled Thin-walled angular thin-walled cells with angular cells cells compact in slight intercellular nature spaces

DISCUSSION The specimen described in this paper differs from almost all species of fossil palm woods known from (see Rao and Menon, 1953; "~ Sahni, 1964) in having peculiar type of fibrovascular bundles. However, a com- parison is still possible, but only with Palmocaulon raoi (Menon, 1964) and Palmoxylon mahabalei (Rao and Menon, in press) whose main features are incorporated in Table I. Palmoeaulon raoi (Menon, 1964), a petrified wood regarded as a petiole, stands comparison with M82 to some limited extent only. Fibrovascular bundles with complete sclerenchymatous sheaths surrounding the vascular elements are found in both. But this is a common feature found in all the bundles of P. raoi, confined to the bundles of the central part only in M3z. The ground parenchyma cells in both the cases are thin-walled and angular. The colour of both the specimens in transverse sections is jet black. In spite of these resemblances, both these specimens are completely different from each other in the distribution, f/v ratio of the fibrovascular bundles and other characters shown in the table. Therefore, d comparison with Pahnoeaulon raoi cannot be entertained. Palmoxylon mahabalei (Rao and Menon, loe. eit.) shows as in Mz2 the cortical and middle Regions. The form of the bundles and their distribution is very similar in both. But the only difference is that the fibrovascular bundles of the central part of thb specimen described in this paper, show a complete sheath of sclerenchyma surrounding the vascular ele~aents. In the case of P, mahabalei this is seen in a few bundles only. It is not advisable 22 Mrss VIMALA K. MENON to lay too much emphasis on the sclerenchyma character also, as,they are likely to vary in one and the same plant at different ages and in different organs. The fibrous bundles are present in the cortical regions of both the species. The ground tissue cells in P. mahabalei are thin-walled rounded cells overlapping each other while in the case of M32 they are thin-walled, angular cells. In view of some of the above resemblances a comparison with P. mahabalei seems to be rather compelling.

A perusal of Table I shows no doubt that the specimen described in this paper bears a close resemblance with P. mahabalei. But it differs from it in being thin and cylindrical with a small portion of the cortex pre- served. It shows that therefore the specimen could not have been much bigger than what it is now even before fossilization. It is more likely that this specimen is a petiole or rachis or inflorescence axis of the palm rather than its stem. But in living palms the inflorescence axis differs from the petiole in having large amount of chambered air-spaces and the presence of a large number of fused bundles. The former feature is absent and the latter is not in sufficiently large numbers, in the specimen described in this paper. It is not unlikely that this specimen represents a petiole of the same species whose wood or perhaps stem may be Palmoxylon mahabalei. But apart from the close similarity of bundle structure and their arrangement there are not many other evidences to show that this was definitely the petiole of P. mahabalei. In view of this it was thought that the specimen may be referred to a non- committal petiole genus Palmocaulon and designated as Palmocaulon maha- balei. The differences noted in the f/v ratio and diameter of the bundles between Palmoxylon mahabalei and the present specimen could be due to the fact that one is a stem while the other is a petiole (Table 1).

DIAGNOSIS Slender petrified axis with cortical and peripheral regions preserved. Cortical region.--Fibrovascular bundles regularly orientaled, dorsal and ventral sclerenchyma sheaths well developed, separated from each other by ground tissue. Xylem vessels mostly one; f/v ratio 0.8/1 to 1.4/1, dia- meter 0.28 to 0.5ram. Fibrous bundles present, stegmata and radiativg or tabular parenchyma absent. Ground tissue not well preserved. Peripheral part.--Fibrovascular bundles regular in orientation, slightly widely distributed, rounded to oval in shape; ventral sclerenchyma many times bigger than dorsal, separated from it by ground tissue, ,xylem vessel one; f/v ratio 0.8/1 tO 1.7/1 diameter 0.19 to 0"31 ram, Fibrous bundles~ Petrified Palm Petiole from Mohgaon Kalan Area, Madhya Pradesh 23 radiating and tabular parenchyma absent. Diminutive bundles present. Ground tissue thin-walled, isodiametric angular cells.

Central part.--Fibrovascular bundles irregular in orientation, closely placed in distribution; rounded to oval, sometimes compressed. Both ventral and dorsal sclerenchyma joined together as a complete sheath around the vascular elements. Xylem vessel one in the centre. Ground tissue similar to that of the lzeripheral part. Locality .. Mohgaon Kalan, District. Age .. Eocene. Type specimen .. M3~, kept in the Department of Botany, University of Lucknow.

SUMMARY A petrified specimen probably a part of a petiole or rachis and showing affinities with Palmoxylon mahabalei is described and referred to the petiole genus Palmocaulon and designated rs Palmocaulon mahabalei. According to Prof. Sahni's classification (1943) which is based upon the combined scheme of Von Mohl (1845 and 1849), and Stenzel (1904), this specimen may probably be kept under the section Cocos-like Palms.

ACKNOWLEDGEMENTS I am deeply indebted to Prof. A. R. Rao for his valuable guidance and critical suggestions during the course of this investigation. I am also grateful to the authorities of the Birbal Sahni Institute of Palaeobotany, Lucknow, for permission to consult their library.

REFERENCES

Mohl, Hugo Von "Ueber den Bau des Palmenstammes (transl. from Mohl in Martius, Genera et species Palmarum). Vermischte schdften botanischen Inhalts," Tiibingen, 1845, 11, 129-85. On the Structure of ,he Palm Stem. English translation published by the Ray Soeiety, London, 1849. Menon, V. K. "Pahnocaulon raoi possibly a new species of petrified palm petiole from Mohgaon Kalan area in Madhya Pradesh," Proc. nat. Inst. Sci., 1964, 30(1), 15-24. Rao, A. R. and Menon, V. K... "Palmoxylon maheshwarii--A petrified palm wood from the Deccan Intertrappean beds," Proc. nat. Inst. Sci., 1963, 29 (4), 423-33. 24 M~ss V1MALA K. MENON

Rao, A. R. and Menon, V.K. "Palmoxylon mahabalei sp. nov., a new petrified palm wood from Mohgaon Kalan, India" (in Press). Sahni, B. .. "A new species of petrified palm stems, Palmoxylon sclero- dermum sp. nov. from the Deccan Intertrappean series," dour. Indian bot. Soc., 1943, 22(2-4), 209-24. t "Revisions of Indian Fossil palms. Part III. Monocoty- ledons," Monogr. Birbal Sahni Inst. Palaeobot., 1964, 1,1-89. Stenzel, K. G. "Fossile PalmenhSlzer," Palaeontologie und Geologie Oster- reich-Ungarns und des orients, 1904, 16, 107-287.

EXPLANATION OF PLATE 1

PHOTO 1. Type specimen before sectioning, ×0.71. PHOTO 2. Transverse section of the specimen showing the detached portion, indicated by an arrow, ×3. PHOTO 3. Distribution of fibrovascular bundles from the cortex, x 38.1. PHOTO 4. Distribution of fibrovascular bundles from the peripheral part, ×40"2. PHOTO 5. Enlarged fibrovascular bundles of the peripheral part, × 19.1. PHOTO 6. Distribution of fibrovascular bundles from the central part, ×36.2. PIaoro 7. Longitudinal section of the specimen showing scalariform pitting of the xylem, × 16.95.

cb, cortical bundle; dsc, dorsal sclerenchyma; fib, fibrovascular bundle; gp, ground parenchyma; lb, lobed bundle; vsc, ventral sclerenchyma. Miss Vimala K. Menon Proc. Incl. Acad. Sci., B, Vol. LXII, P1. !

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FIGS. 1-7