" ¥ 
Sa ; . \ 
aa Special Morphology and Classification. 309 
‘usually separated from the cortical and medullary cells 
by a vascular bundle-sheath, consisting of prosenchymatous 
cells thickened on one or on all sides, and generally fibri- 
Fic. 436.—Black spleenwort, Asplenium Adiantum-nigrum, showing a part of the 
rhizome (natural size, with a single pinna magnified). 
