XXX] DOLEROPHYLLUM 135 



of elliptical or spherical form often loosely attached owing to the 

 well-developed system of intercellular spaces. The lower epi- 

 dermis, assuming that the outer face of the rolled leaves is the 

 morphologically lower surface, forms a uniform layer of palisade 

 cells characterised by their free conical ends (fig. 431, A, B, e) 

 'Which in some obhque sections appear as sharply pointed papillae 

 with almost filiform apices; but while the cells were doubtless 

 papillose Uke those of the epidermis of a velvety petal, the pointed 

 form is due in part to the greater distinctness of the dark contents 

 as compared with the lighter cell-walls. The upper epidermis 

 is much less distinct; it consists of smaller flattened cells with 

 occasional stomata. Renault^ figures a specimen with stomata 

 in a better state of preservation. The vascular bundles are 

 rendered conspicuous by large secretory cells on the lower side, 

 in the larger veins in the form of an arc or irregular group (fig. 

 432, A), but in the finer veins as single cells (fig. 431; A, B). These 

 sacs resemble the tannin cells accompanjdng the veins in a leaf 

 of Ginkgo {cf. fig. 631, G). The xylem- elements are of two kinds, 

 (i) elongated spiral and scalariform conducting elements, forming 

 a vertical plate of a few rows in the larger veins (figs. 431, 432) 

 or a small compact group in the more slender veins (fig. 413, A, B) ; 

 (ii)- much larger isodiametric cells with reticulate or spiral 

 thickening resembhng the transfusion-tracheids of Conifers or, 

 perhaps more closely, similar elements in the leaves of Lepido- 

 dendron. These short tracheids are especially abundant on the 

 flanks of the conducting tracheids (figs. 431, t; 432, A, t), but 

 they sometimes form a complete investment. In the obliquely 

 cut vein reproduced in fig. 431, D, the transfusion-tracheids are 

 abundant : a few are enlarged in fig. 431, E. In the smaller veins 

 (fig. 431, A, B) they are represented by the larger elements, t, 

 on the sides of the conducting strands. The protoxylem lies 

 close to the upper edge in the middle hne {px, figs. 431, A ; 432, A) ; 

 it is difficult to determine its precise position, but it would seem 

 to be slightly internal, the bundle being not quite endarch. No 

 phloem was recognised in the British Museum specimen, but it 

 presumably occurred, if present, where the black patch is shown 



1 Renault (96) A. p. 265, fig. 43. 



