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Life and Time of Indian Williamsonia

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Life and Time of Indian Williamsonia Life and time of Indian Williamsonia )ayasri Banerji Banerji, J 1992. Life and time of Indian Williamsonia. Palaeobotanist 40 : 245-259. The Williamsonia plant, belonging to the order Bennettitales, consists of stem-Bucklandia Presl, leaf­ Ptilophyllum Morris, male flower- Weltrichia Braun and female flower- Williamsonia Carruthers. This plant was perhaps a small, much branched woody tree of xerophytic environment. It co-existed alongwith extremely variable and rich flora including highly diversified plant groups from algae to gymnosperms. In India, it appeared during the marine Jurassic, proliferated and widely distributed in the Lower Cretaceous and disappeared from the vegetational scenario of Upper Cretaceous Period with the advent of angiosperms. Key-words-Bennettitales, Williamsonia, Jurassic-Cretaceous (India). jayasri Baner}i, Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow 226007, India. ri~T ~ 'lfmftq- fili'<1QQ«lf.:lQi "" om~~ "l?li'O'$i'OI<1fl \f>'f it ~ filf<1QQ«lf.:lQi qtfr if ~ ~ 3!<'flT-3!<'flT 'lTIif it ~ "lTif t W'I'T CAT-~ m, ~ ~ ~it ~fu;m;;mrr~1 ~qtm~~ <ffir ll~<'ilf4>~<'1'i"li'tfGr, "''!'''l ~~?l~Ti:t>Qi <ilf.1 'I"lT filf<1QQ«lf.:lQi ~ ~ ~ f;;ru-if.~ ~ 61'1'~dOl'h\'i if m <'IT<'1T ~ Wc:r, 3!fuq,iffiliOlT3if it ~ ¥i "IT' ~ it il'1f4ff1"1ld, it if qtfr ~ 'it, q;r tt ~ ~tl W'I'T~~'-I'<"1if~~3lT, 3Tahmm'-l'<"1if~~~-~'d"f~<f"lT'3'1f'<mm~ ~ ~ ~ ~ if qtm if if t1T"f -flT"f lIT lfllT' LIFE OF WILLIAMSONIA PLANT B. dichotoma Sharma. In B. indica Seward, the secondary wood is more compact than recent cycads In the Upper Mesozoic Era, a new group of and cycadeoids. The medullary rays are uniseriate plants-the Bennettitales, developed that colonised and 'tracheids have multiseriate bordered pits on various habitats of terrestrial areas. This group their radial walls instead of scalariform pitting in the continued till Early Cretaceous. In India, it is majority of cycadeoid stems. Secretory canals are represented by the members of the family abundant in the parenchymatous ground tissue, the Williamsoniaceae and occurs pre-dominantly during cambium and phloem are not preserved. The cross Lower Cretaceous Period (Text-figure 1). The section (Text-figure 2) of B. sahnii Bose 1953a Williamsonia plant is known through its stem­ shows well-defined growth rings in the secondary Bucklandia Presl, leaf-Ptilophyllum Morris, male wood, 4-9 cell thick cork cambium present outside flower- Weltrichia Braun, and Williamsonia the cortex. Cortex is fairly wide, parenchymatous Carruthers female flower. with thick-walled cells, Singly or in group and leaf traces with a single bundle which finally breaks up Stem-Bucklandia Presl into 5-7 strands. Pericycle is with few layers of polygonal cells. The phloem ring is marked by The Bucklandia stem was erect and cylindrical, alternate bands of poorly developed rays leaving big protected by armour of rhomboidal leaf-bases. Four species of Bucklandia described from India are: B. Four Decades of Indian Palaeobotany indica Seward, B. sahnii Bose, B. guptai Sharma and Editors: B S. Venkalillchala & H P. Singh Publisher: Birbal Sahni lnsliwre of Palaeobotany, Lucknow 246 THE PALAEOBOTANIST t \ 'fNr'~ Il.l,·1 U ~ ~ ~\~,rrJllf;·~'""~·i-" I!/~"~,~Iil .• ".••.. ~ \\\~; ~«~\)'}?-;: ~.\I\,II~ I - . .e::::..-- II \'~/ .os • (I(lrj"'0::;:/:/':~ m" ~;.J)J 1r11J~ ~ """"''''', ~~/' - ......" ...."H"~ __ ''-'" ~. "<llI'":""~ III.~ II~j~""""SOH"~ I11(AOPS C\, , If'/ .\:> \)'w J....8 ...lF'UA "y '%").,," :~~" . ~ /.;; ~~V) ~ . r::: fA &:\ ~:'~~:~ ~ ESl\~' ,-!-~~",: -:." ~I \ ~ ~ ~ '( ..\\' . " ':< y~ ~~:::-. ,!;, ::=.-::. ~l '1:f~ .... HTR!CI1I ..... SANTAlENSIS ,:"$.'",1 ,$\\~, - ''I .\ :..I:~.;.~.;~~ \ ,.:/i),.,;r 11\,":' ~·b (c\~ ) I ( ,',': WILLlAI'ISOHl,l tHOIC ..... Il.t{~,,,· '-. : ~;/; . " /,' ",I, I) III \ 'IillJ1b(HI..... "ALDAOlSlS .?01:,~( It(lTll<J1"""'" :~;" \",,',: ;1 "I ., ) (~ wrUItIOlLA PClYA.JOlA Text-figure I-Distribution of Indian Williamsonian flowers. cavirics. Phloem consists of alternate thick- and thin­ cortex. In B. sahnii the stem had forked branches walled elements. Traces of cambium are seen below and the flowers were borne at the point of the phloem. The tracheids of early wood have a large bifurcation as in Wielandiella angustifolia Nathorst. diameter with a thinner wall than those of the late Bucklandia guptai Sharma 1967 has sparsely wood. The late wood is remarkably developed and arranged symmetrical leaf basis and anatomically it occupies about two-third of the whole growth rings. shows the presence of numerous growth rings and Radial surface of the late wood tracheids have nOt so mostly uniseriate medullary rays which are rarely variable pitting but the early wood shows different biseriate. B dichotoma Sharma 1969b is type of pitting from scalariform to multiseriate. Ray characterised by haVing longer rays, biseriate in cells in radial view are rectangular and much wider nature and bordered pits with narrow elliptical pit than high: The pits in the field are bordered, usually pores. According to Bose (1974, p. 196), this species one to six or more, oval or circular in shape. is based on variable characters and these should not Longitudinal section shows that the inner-most part be used for specific differemiation. Besides, he of xylem ring consists of 4 to 8 layers of slender considers it perhaps as a young stem. tracheids with spiral thickening in their walls. Pith is Mode of branching-Seward (1912), while very wide and consists of parenchymatous cells with describing petrified Williamsonia from Scotland, numerous scattered thick-walled cells similar to the suggested the existence of a sympodial branching, BANERJI-LIFE AND TIME OF INDlAN WILLIAMSONIA 247 A Text-figure 2-A, Bucklandia-slem; B, T.S. of Bucklandia-slem. while Sahni (1932) suggested monopodia I stomata except on the marginal region. In P. distans branching in W. sewardiana. jacob & jacob 1954 pinnae have acute apices and the lower cuticle is differentiated into broad stomatiferous and narrow non-stomatiferous bands, Leaf- Pttlopbyllum Morris cells are devoid of papillae and the outer wall of the subsidiary cells is looped. P. jabalpurensis jacob & The genus Ptilophyllum Morris in Grant (1840) jacob 1954 is characterised in having 1-3 papillate originally comprised pinnate fronds, pinnae with marginal cells and papillae are solid circular or acute or obtuse apices. The circumscription of the semi-circular, hollow-circular or crescent-shaped. In genus was later enlarged to include pinnate frond, P. nzpanica Vishnu-Mittre 1956 lower epidermis has pinnae linear-falcate in shape with acute, sub-acute non-papillate cells and stomata are arranged in to obtuse apices, basal acroscopic margin round, bands_ P. gladiatum Bose & Sukh-Dev 1958 is basal basiscopic margin decurrent and veins sub­ distinct in having gladius-like pinnae and non­ parallel to slightly diverging towards the apical papillate epidermal cells of veins and subsidialY margin. The rachis contains a double arc of collateral cells. P. institacallum Bose 1959 is significant in vascular bundles comparable to the pteridosperms possessing papillae of various shapes. The epidermal (Text-figure 3). Sclerenchymatous patches and cells of lower cuticle and stomata are irregularly sclereids are found in the cortex. Single bundle scattered in the inner zone. P. sakrigaliensi$ Sah arises from the upper corner of the double arc of 1958 has elongated pinnae with acute apices. Lower vascular bundle of rachis which divides into two at cuticle is studded with stomata arranged in bands. the base of the pinna. It is repeatedly forked at One or two papillae are present on each epidermal different levels to form a more or less parallel cell of the vein band. P. horridum Roy 1967 shows venations. lower cuticle with stomata in bands and two or more The anatomy of pinna shows collateral, exarch papillae on each epidermal cell of the vein band but xylem with a parenchymatous bundle sheath. they do not form a frill-like structure over the vein Sclereids occur isolated or in groups in the palisade band as in P. institacallum. P. sahnii Gupta & and spongy mesophyll. The salient features of the Sharma 1968 has small pinnae, oblong or oval in cuticle of Ptilophyllum leaves are hypostomatic shape with obtuse apices, lower cuticle is condition with syndetocheilic stomata, but vary in differentiated into broader stomatal, narrow non­ the pattern of distribution of stomata, papillae and stomatal band and marginal non-stomatal region, its morphological differences, being the main epidermal and subsidiary cells are devoid of criteria for ·speciation. P. acutifolium Morris has papillae. P. amarjolense Bose 1953b is distinguished pinnae with acute apices, whereas P. cutchense by its broader leaves and stomatal bands are 4-5 Morris possesses sub-acute to obtuse apices. P. stomata broad. rarinervis (Feistmantel) Bose has pinnae with 2-3 veins only. P. tenerrimum Feistmantel has narrow, Male flower- Weltricbia Braun long pinnae. In P. indicum jacob & jacob 1954, stomata are distributed in stomatal bands. P. oldhami The male flower is characterised by haVing jacob & jacob 1954 shows irregular distribution of microsporophylls forming a cup-shaped structure at 248 THE PALAEOBOTANIST o ~, ------ °0 ;~;::;:;~" ~WJUf& @1~ Sclereid A ~ ~~ Sp,"" .",phyll ~::l~;m )~~' -- Bundle sheath Guard cell 'i II c Subsidiary cell B Xylem ~ Phloem ~"Q Text-figure 3-A, Ptilophyllum-pinna showing venation; 8, Pti/ophyllum leaf; C, T.S. of pinna; D, T.S. of rachis. the base. They bear polleniferous appendages expansion of the lamina. Sharma 0969a) suggested adaxially or distally. Each appendage has two rows of that there are twO whorls, the outer whorl consists of pollen chambers. The pollen grains are oval and 20 sterile bracts and the inner whorl has 20 twisted monocolpate. microsporophylls. He also opines that the From India, male flower was first described as appendages are in twO rows on the adaxial side of Williamsonia santalensis Sitholey & Bose 1953. the proximal part of the microsporophyll and there Later, Bose (1967) suggested that the specimen of is only one row on the distal part of the Williamsonia santalensis be included under the microsporophyll (Text-figure LlC).
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