1 82 Gibson . — Contributions towards a Knowledge 
and endodermis, and showing that the annular cuticularization 
of the endodermal cells is, after all, only a special form of 
cuticularization following on the peculiar conditions under 
which these cells are developed in the mature stem. 
44. Selaginella Wallichii, Spr. Baker’s Handbook, No. 215. 
The structure of the stem in this beautiful species 
resembles fundamentally that of S'. inaeqnalifolia ; the steles 
are, however (save in very large stems), simple, that is to say, 
without any accessory steles. In dissecting out the stelic 
system of a primary shoot, one finds a pretty constant method 
of fusion of leaf-traces and marginal protoxylems. Each of 
the simple branches has one stele ; the main axis has three, 
which may be traced right up to the growing-point, at least in 
procambial form (PI. XI, Fig. 60). The inner marginal proto- 
xylem of the branch stele fuses with the inner marginal pro- 
toxylem of the dorsal stele, the outer fuses with the adjacent 
marginal protoxylem of the median axis stele. This is what one 
would expect on the analogy of the mode of origin of the 
dorsal cord of S. uncinata . The ventral stele is composed of the 
fused leaf-traces of the axillary leaves. In older branchings, 
where the two axes each have three steles, the mode of union 
is precisely that already described for S. inaequalifolia. The 
ordinary leaf-traces are inserted on the margins of the median 
stele only. 
The primary creeping stems are at first monostelic as in the 
last described species. 
There is a distinct cuticle and epidermis, and five to six 
layers of stereome, followed by an abundant thick-walled 
cortex, the cells of which become thinner walled inwards. The 
lacunae are sharply marked off. The inner cortex is covered 
by small elongated creeping cells, starting from definite 
regions. Some of these articulate with endodermal cells 
o 
(PI. X, Figs. 56-58). The pericycle is two to three layers 
deep, and there are many protophloem-elements. The sieve- 
tubes are in two layers, dorsally and ventrally, and one (often 
interrupted) at the margins. One irregular layer of paren- 
chyma separates the xylem from the sieve-tube layer. There 
