10 Development of the Fern Leaf 
becomes compound later, or whether it is compound from the 
first. 
The development of the form of the leaf that is simple at 
first and remains simple, while obviously differing in different 
species according to the phases through which the leaf passes 
and the ultimate form to be produced, need not be described 
here. 
The development of the form of the leaf that is simple at first 
and becomes compound later, and of the form of the leaf that is 
compound from the first, can be best understood by ascertaining 
the various ways in which simple leaves become compound and 
compound leaves more so. In the following description of the 
ways in which this occurs in our northeastern ferns, for the sake 
of brevity, each of the various processes will be described as if 
continuous and taking place in a single leaf, but the reader will 
bear in mind that in reality each is exemplified in a series of 
leaves. 
The student of actual specimens illustrating these processes 
will find it necessary to bear in mind also that, (1) as the com- 
plete series of leaves is not likely to be borne by any one plant, 
and (2) as it could scarcely be considered remarkable if 
some steps in any one of the processes, although portrayed at 
first, should in the course of time come to be partly or wholly 
obliterated, as a rule, in the series borne by the plants of a species, 
hence, (3) that failure to find some steps portrayed in the series 
borne by one plant, or even in the series borne by many plants 
of a species, which often occurs, does not necessarily mean that 
these steps are not portrayed at the time or have not been por- 
trayed at some former time in the series borne by any plant of 
