GENERA AND SPECIES. Tt. 
PLATE XII. 
PELLAA. Link. 
CLIFF-BRAKE FERN. 
GEN. CHAR.—Fruit-dots in elongated patches on the upper part 
of the veins; indusium membranaceous, continuous, formed of the 
reflexed margin; stipes dark colored. 
This genus has a great resemblance to Pteris, and was 
formerly embraced in that genus. But it is evidently dis- 
tinct. In the Pella the sporangia are arranged in elongated 
clusters at the ends of free veins. This is well exhibited 
in the young fertile frond; but, as the plant grows and 
reaches maturity, the clusters of sporangia are distributed 
in a linear order along the reflexed margin of the pinnule, 
forming a continuous line as in the genus Pteris. Near the 
apex of the leaflet it has a somewhat transparent, mem- 
branaceous border, which, toward the base, is folded over, 
and forms, with the re-curved margin of the pinnule, the 
covering or indusium. 
This genus is sometimes confounded with Allosorus 
(Bernhardi), to which it is very nearly related. There are 
ten species in the United States, mostly found in the 
Pacific States and New Mexico; but one is indigenous 
to Kentucky. 
I have attempted to show, in the magnified pinnule rep- 
resented in the illustration, the characteristic nature of the 
veins and of the indusium. 
