Development of the Fern Leaf 19 
In the leaf with pinnate anastomose venation, the incisions by 
means of which segments are formed occur, as in the leaf with 
pinnate free venation, between the primary branches of the leaf’s 
midveins, and the midveins of each of these segments start, as 
in the latter leaf, from the primary branch, as a base, contained 
within the segment. 
In Fig. 5 is shown the section of a leaf with pinnate anasto- 
mose venation in which segments have begun to form, with the 
midveins of these segments 
not yet evident. In Fig. 6 
is shown a longitudinal sec- 
tion of the segment of a leaf 
with similar venation, partly 

Fic. 5. 
formed segments on one side of the midvein, and the midveins 
of these segments evident. 
In the leaves with free flabellate venation, each simple leaf- 
blade and each segment of each compound leaf-blade is entered 
at base by a vein which, instead of forming a midvein, either 
forks once or is dissipated into forking veinlets: if the latter, 
the successive veinlets, excepting the two first, which are formed 
by the forking of the primary vein, are formed by the forking of 
the veinlets preceding them. 
Each incision subdividing the simple blade or segment of a 
