the Anatomy of the Genus Selaginella. 461 
vertical strand divides into an upper part which goes to the 
upper root and a lower part which goes to the lower and 
functional root ( 6 , 7 ). As in 5. Helvetica, the upper and 
middle steles of the stem, before giving off the strands to the 
vertical band which supplies the roots, become centroxylic 
on that side, again becoming perixylic when the root- 
strands are isolated. 
In S. Wallichii , Spr., the roots are very short and not 
related in all cases to the branching of the stem, but generally 
arise from the under side of the rhizome just at the junction 
of the minor and major branches, but from the latter. The 
stele of the aerial root in section is similar to that of 5. atro- 
viridis , save that the protoxylem is almost isolated from the 
xylem. The endodermis is well defined, the pericycle is two 
or three layers thick, and there are abundant root-hairs right 
up to the margin of the root-cap. 
In the general anatomy of the root similar features to 
those exhibited by S. Wallichii are shown by S. chilensis , 
Spr., S. viridangida , Spr., .S'. Victoriae , Moore, .S', inaequali - 
folia , Spr., and S. gracilis, Moore. In 5. Willdenowii, Bak., 
the root arises as in S. Wallichii. There is an abortive root 
on the upper side of the stem, which has a small prominence 
of vascular tissue arising from the strand of the functional 
root near its junction with the stele of the stem. The lateral 
branch is isolated farther back. The abortive root, as in 
.S’, inaequalifolia, is sometimes functional. The xylem of the 
root-stele is slightly crescentic, with the protoxylem almost 
isolated from the xylem but accompanied by some meta- 
xylem. The subterranean part of the root is normally 
monarch with a sclerotic cortex and plentiful root-hairs. 
.S', laevigata, Baker, var., Lyallii , Spr., which exhibits so many 
anomalies in its stem-structure, is normal in its root-structure. 
The roots arise singly at the bases of the erect shoots, and 
their vascular strands are inserted on the cylindrical stele of 
the rhizome. 
In S'. Lobbiiy Moore, the only other species which I have 
examined in detail, the roots arise at the forkings of the stem, 
