INDIAN JUEASSIO GTMNOSPERMS 



n 



Yorkshire WilHamsonias, in the Paris Museum *, contains several such axes, certain 

 of which have heen mentioned by Saporta (21, pi. 81. fig. 1), Seward (26, p. 276), and 

 Wieland (38, p. 98 ; 39, p. 448, fig. 6). (Eor further references, see Seward, 27, p. 182; 

 Saporta, 22, pi. 240 to pi. 243.) 



iii. Stems. 



WiLLIAMSONIAN TYPE. 



Block I. shows a portion of a cycadean stem (PI. 9. fig. 4) 10-1 cms. in length and 

 about 5 or 6 cms. in diameter. Part of the fragment shows the armour of leaf -bases 

 with indications of ramental packing between them (PI. 7. fig. 16), while part has the 

 outer cortical parts broken away, exposing the stele. At the widest part of the stem 

 is a scar (PI. 9. fig. 4, a ; PI. 7. fig. 14), evidently of a lateral structure which has 

 completely fallen away. Below it the wood is badly shattered, and it is impossible to 

 discover how the branch was supplied with vascular elements. There are no indications 

 as to the nature of this lateral branch which may have been vegetative or reproductive. 

 The presence of bract-like structures surrounding the region of the scar (PI. 7. figs. 14 

 & 15) suggests the possibility that it was left by a bract-bearing floral axis. 



Owing to the absence of a large part of the armour, it is not possible to determine 

 with certainty whether there are zones of large and small leaf-scars, though towards 

 the lower end of the stem-fragment the few remaining scars are large, and longer than 

 they are broad ; while in the region of the scar they are small, and broader than long 

 (PL 9. fig. 4 J. All the scars are, however, more or less rhomboidal to lozenge-shaped 



(19, p. 36). 



In the lower part of the stem there is a large weathered leaf -base, showing seven 



slight depressions, representing the vascular bundles of the leaf -supply. The vascular 

 bundles correspond in position to those of the leaf-base sections, there being two adaxial, 

 three abaxial, and two more or less lateral (PI. 7. fig. 17 « & ^^ ; cf. fig. 17 c, an example 

 of a transversely broken leaf-base; also PL 9. fig. 8, a section of a leaf- base). The 

 reverse of several leaf-bases, below the actual stem, shows the same occurrence of seven 



vascular bundles passing out to the leaf. 



Cut surfaces and thin sections reveal the general structure of the stem and the leaf- 

 bases (PL 8. figs. 8-15 ; PL 9. fig. 8). In transverse section, two or three series of 

 leaf -bases are seen surrounding the stem. These possess an outer epidermis, a fairly broad 

 peripheral layer of sclerenchyma, and an inner ground-mass of parenchyma with many 

 secretory sacs. There are constantly seven vascular bundles arranged as in the diagram, 

 the xylem being directed inward (PL 7. fig. 18 ; cf. arrangement in the weathered leaf- 

 base). There is no indication of the expected mesarch structure of the vascular bundles, 

 but it is probable that the protoxylem and centripetal xylem are not preserved, and 

 that the mass of radially arranged elements seen in the most favourable cases is all 



• 



Part of this collection has recently heen acquired hy Yale University 



SECOND SEEIES. — BOTANY, VOL. VIII. 



M 



