Polypody 53 
segments sometimes is once-forked and bears a sorus at each of 
its two apices. The presence of both these sori can, however, be 
accounted for. The presence of the sorus on the veinlet nearest 
the segment’s midvein is explained, if that veinlet is regarded 
as the superior basal primary branch of the primary branch of 
the segment’s midvein. The presence of the sorus on the other 
veinlet also is explained, if this veinlet is regarded as merely an 
extension of the superior basal primary branch of the seg- 
ment’s midvein, and so (since the segment’s midvein is a pri- 
mary branch of the leaf’s primary midvein), as a part of the 
superior basal primary branch of a primary branch of the pri- 
mary midvein. Occasionally the two veinlets become connivent 
at apex, and the two sori coalesce, forming one, which is borne on 
the veinlet’s connivent apices. 
Sometimes occasional areole occur in the leaf at various 
stages of its development. 
The veins are clubbed at apex and appear to pierce the face 
of the leaf: their tips are visible as stramineous spots on the 
leaf’s upper surface at every stage of leaf-development. 
The leaf often becomes monstrously developed. ‘Var. Cam- 
bricum” Moore, and many other so-called varieties of this species, 
are based upon monstrously developed forms of the leaf. 
