2 Development of the Fern Leaf 
the sum of the stages of development of the form and venation of 
the leaf in each species, than with knowledge of isolated stages, 
however advanced, alone. This is especially true if, as there 
seems reason to believe,* traces of each of these plants’ descent 
are to be seen in phases of the plant’s leaf during its develop- 
ment. 
Most fern students, however, cannot easily obtain more than 
isolated and, usually, mature stages. It seems, then, worth while 
to ascertain, if possible, both the various modes of development 
of form and venation in fern leaves, and the various effects pro- 
duced by these in the leaves, in order that the modes of this 
development in any species’ leaf may be recognized from isolated 
stages of the leaf, and a working knowledge of the missing stages 
thus gained. 
It is proposed to outline in this chapter the different modes of 
this development, as shown in the fern species of the northeastern 
United States, and to point out in succeeding chapters various 
effects produced by these in the leaves of certain of the species. 
Such species have been included as serve to represent a wide 
diversity of effects. While the account contained in this chapter 
is based principally on specimens of the species of the northeastern 
States, it has been confirmed on examination of very many speci- 
mens of other species. 
The development of the fern species’ leaf from the first to 
the adult stage is exemplified, as fern students know, not in a 
single leaf, but in a series of leaves. This series is borne by the 
fern-plant, which is technically known as the sporophyte. The 
leaves of the series, which begins with the first leaf produced by 
= Seespais- 
