Palmoxylon </Emphasis> from the Deccan Intertrappean Beds

A NEW SPECIES OF PALMOXYLON FROM THE DECCAN INTERTRAPPEAN BEDS BY MISS VIMALA K. MENON (Department of Botany, University of Lucknow) Received October 3, 1963 (Commtmieated by Prof. L. Narayana Rao, v.A.ac.) INTRODUCTION THE specimen described here is one of the many fragments of silicified palm woods collected from Mohgaon Kalan area, Madhya Pradesh, a locality from which a number of petrified palm woods have been described. The specimen is fragmentary but measuring about 6- 5 cm. in length and 3 -4 cm. in breadth. The preservation is not quite satisfactory, yet the arrangement of the bundles in the different zones of the wood is very clear to the naked eye on the polished surface of the specimen. The specimen is brownish-yellow in colour. In thin sections the yellow portions look white. ANATOMICAL DESCRIPTIONS Transverse sections of the specimen show three distinct zones--the Dermal, Sub-dermal and Central (Plate II, Photo 1). Fortunately, a small portion of th~ cortex also is preserved on the outside of these zones. Thin sections of the cortical region show mainly fibrous bundles. They are of varying sizes and irregularly distributed (Fig. 1). The ground tissue is compactly arranged, with thin-walled cells. Dermal zone consists of fibrovascular bundles regularly orientated and closely placed (Fig. 2 ; Plate II, P~oto 2). The row of bundles just belo wthecor- tex isvery small in size and are more orless round to oval inshape (Figs. 3-5). The rest of the bundles are elongated (Figs. 6-13). In between these elongated bundles are seen some smaller bundles (Figs. 14 and 15). The frequency of the bundles is 245 to 320 per cm. ~ and they are about 0-2-0-5ram. in diameter. The bundles are Very crowded, so that they leave very little space for the ground tissue. And even this.is very compact in nature with some intercellular spaces. Thef/v ratio in the main bundles is about 0"5/1-1.4/1. The auricular lobes are round and the median sinus is concave. Phloem is preserved in some of the bundles. The vascular part consists mostly of 77 78 Miss VIMALA K, MENON 'i¢ 21 1 25 FIGS. 1-25. Fig. 1. Transverse section of the cortical region showing the fibrou bundles and the ground tissue, x 56. fb, fibrous bundles. Fig. 2. Distribution of th~ fibrovasculat bundles in the dermal zone, x 36. eb, crushed bundle. Figs. 3-5. Smaller bundles in tho region below the cortex, ×60. Figs. 6-15. Different kinds of bundles in the dermal zone, x60. Fig. 16. Distribution of the fibrovascular bundles in the sub-dermal zone, x 36. Fi~. 17-23. Different kinds of bundles in the sub-dermal zone, x 60. Fig. 24. One fibrovascular bundle of the sub-dermal zone showing the grouped xylem vessels, x 60. Fig. 25. One fused bundl~ )howi~ tho fmio= on tl~ vascul~ part, x C30. A New Speoies of Palmoxylon from the Deccan Intertrappean Beds 79 one main xylem vessel (Figs. 6-10) but sometimes a pair of vessels lying side by side (Figs. 11 and 12). Protoxylem is present. The vessels are ccmpletely excluded or are outside the median sinus. There is no radiating or tabular parenchyma seen around the fibrovascular bundles. Sub-dermal zone.--The majority of the fibrovascular bundles are regularly orientated and are less densely crowded (Fig. 16; Plate II, Fhoto 3). They are 150-170 per cm. °- and are of different sizes and ,~hapes (Figs. 17-23). The bundles are 0" 3-0.6 mm. in diameter and their fly ratio varies from 0.4/1-1/1. The auricular lobes are mostly round, the median sinus is concave to somewhat fiat (Figs. 17-23). Usually, there are two big, circular to oval main vessels, excluded, placed side by side in the vascular parts of the bundles (Figs. 18-23). Some of the bundles consist of a numl:er of xylem vessels grouped tcgelher (Fig. 24). This type of bundles are seen in all the three zones. Smaller rounded bundles occur in between the olher main bundles (Fig. 22). Radiat- ing and tabular parenchyma cells surrounding the bundles are totally absent. Here and there are found some fused bundles. Their fusion takes place either in the sclerenchyma parts or in the vascular parts (Figs. 25 and 26). Leaf-traces are often found in this zone. They are bigger lhan the main bundles (Fig. 27). Central zone is distinguished by the irregular orientation of the fibre- vascular bundles (Fig. 28 ; Plate II, Fhoto 4) and lhey are far apart from each other. They are 80--125 per cm. 2 and are 0.5-0-8 ram. in diameter. The varying form of bundles is seen in Figs. 29-33. The fly rati 9 of the bundles is 0.3/1-0.8/1. The median sinus is somewhat concave and auricular lobes are round. Rounded, excluded, paired vessels occur more commonly in the vascular parts of the bundles (Figs. 30, 31 and 33; Plate III, Photo 5). In between the big bundles there occur occasionally a few small fibrovascular bundles. Radiating or tabular parenchyma cells are conspicuous by their absence. Leaf-trace bundles are very common here (Fig. 34). Fibrous bundles are present only in the cortex. They are altogether absent in the other three zones. Stegmata also have not been observed in any of the fibrovascular bundles. Phloem is preserved in most of the bundles in all the three zones. A more or less triangular-shaped phloem cavity is clearly seen in the bundles in which the phloem is not preserved, 80 Mms VI~LA K. MENOI~ dsc xy i Y ' ii::!!i!ii FIos. 26-35. Fig. 26. One fused bundle showing the fusion on the sclerenchyma part, x75. Fig. 27. One leaf-trace bundle of the sub-dermal zone, × 75. Pxy, protoxylem. Fig. 28. Distribution of the bundles in the central zone, x45. Fig. 29-32. Different types of bundles in the central zone, x 75. Fig. 33. One fibrovascular bundle of the central zone showing all the tissues, x75, dse, dorsal sclerenchyma; mxy, metaxylem; P, parenchyma; ph, phloem; pxy, protoxylem. Fig. 34. One leaf-trace bundle of the central zone, x?5. pxj,, "protoxylern. Fi8. 35, A poltion of the ground tissue in the central,zone, x75, A New Species of Paimoxylon from the Deccan Intertrappean Beds $1 The ground tissue is compact throughout the wood (Fig. 35). The cells are thin-walled, oval to rounded in shape with slight intercellular spaces occasionally seen in between them. In the longitudinal sections these cells are seen to be placed contiguously in vertical rows (Plate III, Photo 6) as in other palm woods. There are some special type of cells present in the ground tissue (Plate II, Photos 2-4). The bad preservation makes it difficult to say what they are. They are mostly single-celled structures, but sometimes a chain of five or six cells joined together are also seen. Some of them show bar-like thicken- ings. The nature of these cells could not be determined. But they may be comparable to idioblasts as reported in the case of Palmoxylon sclerodermum by Sahni (1943). Longitudinal sections show the pitting of the xylem vessels is of the multiseriate scalariform as well as typical helical types (Plate III, Photo 6). The perforated end-walls are obliquely placed and show a series of widely spaced parallel bars of thickening (Plate III, Photo 7). DISCUSSION Quite a large number of palm woods have been described from the Deccan Intertrappean beds by several authors (Sahni, 1931, 1943, 1946; Rode, 1933; Shukla, 1939, 1946; Ramanujam, 1953, 1958; Lakhanpal, 1955; Mahabale, 1958; Prakash, 1958; 1961; Rao and Menon, 1962, 1963). The characters of all these palms have been incorporated in a tabular form (Rao and Menon, 1963). The specimen described in the present paper shares some character or other with each one of the species in Table I. The absence or presence of fibrous bundles, stegmata, radiating or tabular parenchyma, posterior sclerenchyma, are some such characters--which may be considered as comparatively unimportant. But a closer comparison can be possible with Palmoxylon puratanam, Palmoxylon narayanai and Palmoxylon mahesb- warii. The specimen described in this paper resembles the above-mentioned three species in a few of the characters, but differs from them in some of the importan t characters, like frequency of the bundles in the various zones of the wood ; fly ratio of the bundles ; and the diameter and nature of the bundles. The number of bundles per cm. ~ in this species is greater than in P. puratanam, P. narayanai and the bundles in the dermal zone of P. maheshwarff but lesser than those in the sub-dermal and ~entral zones. The fly ratio of P. puratanam and P. narayanai is greater than the fly ratio of the specimen described here, while f/v ratio of P. maheshwarii is lesser. As far as the nature, shape and type of the fibrovascular bundles are concerned these four species are quite different from each other. This can be noted easily from the figures and 82 Mms VI~,LA K. M~oN TABLE Diameter Base of the Name of the Frequency f]~ ratio Palmoxylon of of the [ dorsal No. Cortex of the bundles [ sclersn- species the bundles bundles (inmm.) [ chyma Palmoxylom Imperfectly preserved D-80-100/cxa.* D-4/1 D--0.8- Rounded puratanam thin-walled paten- SI~-7.~/cm. t SD-3/2- 0-5 cordate (Ramanujam. chyma calls. Nume- C-20-25/cm. s 1½/1 SD-0.95- median C.

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