192 Gibson. — Contributions towards a Knowledge 
as L epidodendron Harcourtii , With., where also, according to 
Williamson’s researches {Phil. Trans., 1893), there exists 
a central cylindrical stele enclosing a medulla and bearing 
protoxylem-areas on the outer margin of the ring of meta- 
xylem. I have looked in vain for any evidence of secondary 
increase of the xylem in the material I possess of .S'. Lyallii , 
but am hopeful of obtaining ere long much older rhizomes 
from Madagascar which, it is quite possible, may afford some 
evidence of a closer relationship between the modern Sela- 
ginellas and the ancient Lepidodendra than is at present 
forthcoming. I am not aware that any published account has 
hitherto appeared of the existence of such a condition of the 
stele in the Selaginellaceae as that I have described above, 
and it seems to me that the results arrived at ought to have 
an important bearing on the study of the phylogeny of the 
genus. 
Dangeard’s description of the structure of the stem of 
S. Lyallii seems to me very inadequate. He has apparently 
never dissected out the stelic system, nor has he even sus- 
pected a fundamental difference in structure in the rhizome. 
Moreover, he takes the arrangement of steles in the branch as 
equivalent to that of a primary shoot, and entirely omits any 
mention of detailed histology. 
Section II. Comparative Summary. 
Dangeard alone has ventured to give a comparative summary 
of the anatomy of the genus. It will be convenient for future 
reference to outline his views at this point. After a pre- 
liminary summary of the histology which I have criticized in 
the historical introduction to this paper, the author goes on to 
distinguish certain anatomical types as follows : — 
1. The stem possesses four foliar cords, isolated and 
separate. Under this section Dangeard places such forms 
as .S', tdiginosa (a species I have been unable to obtain), 
5. spinosa , and S. rupestris. I have pointed out under the 
two latter species that his description of these is both inaccu- 
