5i5 
the Anatomy of the Genus Selaginella . 
those approaching the vascular bundle are considerably smaller, which makes 
the endodermis less clearly visible. The phloem as well as the xylem 
Fig. XIII, i, 2, S. cusfiidata : i , cross-section of aerial root ; 2, longitudinal section of same. 
. 3, 4, S. pilifera : 3, old rhizophore ; 4, young rhizophore. 
is well developed. The protoxylem is composed of about five tracheides ; 
the metaxylem of ten to fourteen. 
The terrestrial roots are exactly like the former. Roots which are 
developed in a semi-arid desert region have as a rule a cortex which is 
Mm3 
