246 UNDERWOOD: AMERICAN FERNS 
and also at a’a’ ; at the latter points we may have pairs of pecti- 
nate pinnae simply (as shown on the right) or in some species we 
may have a second forking (as shown on the left), or in still other 
species this may be continued still further. Each species when 
| essabece Dist 
Fic. 1. Diagram of method of branching in Dicranopteris. 
normally mature appears to have a definite limit to the number of 
Successive forkings of the same members. So far the problem is 
simple, but see what happens later. At some period the bud at 
