50 
BEAUTIFUL FERNS. 
SO that the pinnae are pod-like, and either sub-cylindrical or 
somewhat moniliform. The venation is free, and the sori are 
dorsal on the veins. Mr. Faxon writes; “The indusium can 
be detected only when the fertile frond is very young, and 
appears as a very delicate, lacerate membrane, attached at the 
base of the receptacle, and serving to separate the sorus from 
its neighbors. I have not found it in any case hood-like as 
in O. sensibilis. The sori are quickly confluent, and all trace 
of the indusium is soon lost. The membranaceous edge of 
the transformed fertile pinna is attached near the bases of the 
inferior sori and a fold is usually found pressed against the 
sori as seen in the drawing (Fig. 3). This is usually ruptured, 
so as to leave a portion attached at the base of the sorus, 
and must not be mistaken for the true indusium, which is 
within.” 
The sporangia have twenty-six or twenty-eight articula- 
tions of the ring. The spores are dark-colored and ovoid. 
Imperfectly fertile fronds are often found, which are anal- 
ogous to the “ obtusilobata ” condition of O. sensibilis. 
