of the Anatomy of the Genus Selaginella , Spr. 201 
a group as the Sannentosae section of the subgenus S tacky- 
gynandrum , which so nearly agrees with the anatomical section 
of which X. inaequalifolia is the type, we find 5. Mettenii 
widely separated from the type and S. W illdenowii refused 
a place. A more prominent case, however, is that of S. Lyallii , 
which, although it has a quite unique anatomical structure, 
stands side by side with species like .S'. Vogelii and S.grandis, 
forms not separable histologically from S. Martensii. How 
far comparative anatomy may serve as a basis for a revision 
of the established classification of the Selaginellaceae, and how 
far it supports or otherwise external morphology, can only 
be determined after extended observation on all the members 
and not the stem only. Meantime I think it worth while to 
draw attention to the fact that anatomy does not support the 
classification based on external morphology, at all events so 
far as the stem-structure of the above-mentioned species is 
concerned. 
EXPLANATION OF FIGURES IN PLATES 
IX, X, XI, AND XII. 
Illustrating Prof. Harvey Gibson’s paper on the Anatomy of Selaginella. 
(The magnification employed is indicated in each case, but the figures in some 
cases have for convenience been reduced). 
PLATE IX. 
Figs. 1-5. S. Martensii , Spr. 
Fig. 1. Dissection of the stele of a primary shoot after treatment with KOH , 
viewed from the dorsal surface. The axillary leaf-trace is indicated by an arrow- 
head. a, the dorsal cord formed by fusion of the adjacent marginal protoxylems 
of branch and chief-axis ( x io). 
Fig. 2. A small portion of the stele in transverse section, a, pericycle; b, sieve- 
tubes ; c, phloem-parenchyma ; d, protophloem-elements ; e , metaxylem-elements 
( x 55°)- 
Fig- 3. tf, b, c , successive stages in the development of the cuticularized endo- 
dermal cell, showing mode of origin of the annulus ( x 800). 
