the Anatomy of the GeniLS Selaginella. 463 
the way along the concave margin of the xylem. The isolation 
of the protoxylem in this species is a peculiar feature which 
I can find no parallel for amongst other members of the genus, 
although the condition is led up to by the semi-isolation of 
the protoxylems in such species as S. Wallickii. 
General Conclusions. 
1. The root of Selaginella is either subterranean only, or 
partly aerial and partly subterranean. 
2. The view held by some authors that the aerial part of 
the root is of cauline value, and should be distinguished from 
the underground portion as a ‘ rhizophore,’ is not supported 
by sufficient morphological, anatomical, or developmental 
evidence. 
3. The root anatomically is monarch, both in its aerial and 
underground regions, with well-defined endodermis. 
The branching of the root is dichotomous, and the first 
dichotomy is at right angles to the long axis of the stem. 
4. In several species the vascular cord of the stem at the 
origin of the root is centroxylic. 
5. A centroxylic condition of the aerial part of the root 
occurs in 5 . Kraussiana , S. delicatissima , and S. Poulteri. 
6 . At every forking of the root the protoxylems of the two 
branch roots face each other, having revolved through an 
angle of 90 degrees. 
7. Certain exceptional positions of the protoxylems are 
also referred to. 
