BORDER SPECIES. 
ESIDES the truly representative spe- 
cies of eastern America, there are 
a few whose centre of distribution 
is beyond our limits but which 
stray far enough over the borders 
to make some mention of them 
desirable. 
The Rock Brake. 
One of the most interesting of the border species is 
the rock brake (Cryptogramma acrostichoides) which 
inhabits the far North. In the East it reaches to 
Labrador and the country north of Lakes Huron and 
Superior, but in the West it is found in Colorado and 
California and extends from thence to the Arctic Circle. 
It is an inhabitant of rocky places, growing in the chinks 
between the stones, often in dense patches. 
The plants are usually from six to eight inches high, 
The stipes of the fertile fronds are about twice as long 
as those of the sterile, so that there are usually two 
tiers of fronds. Both are ovate-oblong in shape, the 
sterile rather thin and twice pinnate with ovate pinne 
and toothed or lobed rounded pinnules, while the fertile 
are three times pinnate, with long, narrow, podlike pin- 
nules, due to the edges being rolled back to the midrib. 
The sporangia are borne in roundish sori near the mar- 
gins which are slightly altered to form the indusium, 
co 
