of the Anatomy of the Genus Selaginella , Spr. 195 
leaf-traces. The leaf-traces on the region of the stem which 
has a stele with central protoxylem pierce the metaxylem and 
fuse with the central protoxylem cord. The cylinder is, how- 
ever, not hollow, although in the apical region the metaxylem 
is preceded by procambial tissue. 
3. S. Galeottei , Spr. 
The so-called bistelic species may be derived from stems 
like those of S'. Lyallii (where the leaves are arranged in four 
rows), by fusion of the protoxylems of adjacent leaf-traces 
and feeble development of metaxylem, so that two laterally 
placed steles result each with one protoxylem strand mar- 
ginally situated. The steles of the chief axis fuse at or near 
the origin of branches, and the two steles of the branch unite 
before their insertion on the stele of that side of the main axis. 
4. S'. Braunii , Baker. 
In this type the creeping axis is differentiated from the 
erect shoots, as in 5 . Lyallii , and is at first monostelic. Later 
it becomes bistelic, the steles being dorsal and ventral, not 
lateral. The erect shoots are, however, monostelic, the two 
marginal protoxylems arising from the dorsal and ventral 
steles respectively. 
5. 5 . oregana, , Eat. 
In this species we have a transition between S'. spmosa 
and the usual Selaginella type ; for here, although the leaves 
are homophyllous, the stele is dorsi-ventral, and consists of 
a ribbon with two marginal protoxylems and one dorsal 
protoxylem formed by fusion of the adjacent marginal proto- 
xylems of branch and axis. 
6. S. Martensii , Spr. 
Round this species may be grouped the majority of the 
species of the genus, diverse as they are in habit, all character- 
ized by dorsiventrality both of external morphological features 
and internal anatomy, and by the possession of a single stele. 
7. S', uncinata , Spr. 
This type is particularly interesting, inasmuch as it gives 
the first indication of the tendency to form at least three 
distinct steles placed dorsally, medianly, and ventrally, and 
