6 Bower. — Studies in the Phytogeny of the Fiti cates. VI. 
subject to profuse perforation. The parenchyma of the rhizome is crowded 
with nests of black sclerenchyma. Sometimes isolated cells are indurated : 
more frequently groups of them. The nests are not continuous longi- 
tudinally, and they extend only a short way up the petiole. They give a 
hard, gritty texture to the whole tissue, as in NeocJieiropteris. 
The leaf-trace a little above the base of the petiole consists usually 
of five strands, the two adaxial being the largest, and occupying the ends of 
the horseshoe curve. In all the modifications which follow in the upward 
course it appears that these strands maintain their independence of one 
another ; that is, there is no fusion between the two ends of the curve, but 
the gap ( + ) remains constantly open. All the changes are in fact variants 
on the curve itself, which is not obliterated by them. This is important for 
comparison on the one hand with Cheiropleuria , and on the other with 
Platycerium. The upward course has been followed in the fertile leaf, and 
the results are shown in Text-fig. 2, i-xvii, all of which are orientated with 
the adaxial face uppermost. Nos. i-vi illustrate the course up the petiole, 
