88 THE CLIFF BRAKES. 
ity is known for it, namely near Durham, Gray county, 
Ontario, 
This species grows in the crevices of rocks in moun- 
tainous districts. The rootstock is rather small, and the 
wiry, purple-brown stipes, several times longer than the 
blades, are densely tufted. The blades are ovate-tri- 
angular in outline, pinnate at the summit and often four 
times pinnate at the base. So great is its tendency to 
fruit that sterile fronds are seldom seen. When they do 
occur, the pinnules are somewhat broader than those of 
the fertile fronds and are sharply serrate. In fruit the 
Marrow pinnules are recurved over the sori in such a 
manner as to have the appearance of sharp-pointed, 
linear, half-open pods. They vary in length from a quar- 
ter to half an inch and are placed very closely together. 
There are upwards of fifty species of Pellga. The ma- 
jority are inhabitants of warm regions. In California 
and the Southwest, there are about a dozen species, all 
found in rocky places. Some grow exposed to the full 
sun and during drouth curl up and become dry and 
brittle. When rain comes again the apparently dead 
fronds unfurl and take up vigorous life once more. The 
generic name is from the Greek and means dusky, in 
allusion to the stipes of most species. 
