of the Anatomy of the Genus Selaginella , Spr. 149 
present paper therefore I employ the terms ‘ pericycle/ ‘ endo- 
dermis/ and ‘ stele/ purely in a descriptive sense . 
Of the 334 species of Selaginella recorded by Baker ( 4 ) 
I have examined fifty- three (not counting numerous varieties) 
in a fresh condition. In the great majority of cases I was 
able to obtain the entire plant— not the erect shoots alone. 
This is of fundamental importance, since, as I shall show later 
on, the procumbent or horizontal axis in very many cases 
differs markedly in structure from the erect axis. I have 
divided the paper into two parts ; the first deals with the 
anatomy and histology of the individual species, the second 
attempts to give a comparative summary of the general 
anatomy and histology. In the first section I have grouped 
the species round certain type-forms which are treated of 
rather more fully. For instance, a large number of species 
are closely related to S'. Martensii , all characterized by the 
possession of a dorsiventral axis and a single ribbon-shaped 
stele. Since these are the forms most fully investigated 
I have dealt with them first. S', oregana serves as the type 
of that section which is characterized by having homophyllous 
leaves and yet a ribbon-shaped dorsiventral stele. Certain 
anomalous monostelic forms are then discussed, such as 
S', spinosa , S. Braunii , &c. The bistelic species are asso- 
ciated with S'. Galeottei as the type, and the tristelic species 
with S. inaequalifolia. S. Lyallii , perhaps the most aberrant 
of all, I have dealt with in a special section. 
Section I. Anatomy of Species. 
A. Martensii Type. 
1. Selaginella Martensii, Spr. Bakers Handbook, No. 179. 
The stem of this well-known and often investigated 
species is partly trailing, partly ascending, but in all parts 
dorsiventral. One ribbon-shaped stele runs throughout the 
axis, lying in a lacuna sharply marked off by siliceous deposit 
