26 Development of the Fern Leaf 
subdivide, and upon the extent to which this subdivision is car- 
ried, in the course of the leaf’s development. 
Instances sometimes occur in which some part of a species’ 
leaf that normally is undivided becomes subdivided into seg- 
ments, and one, or repeated, series of segments may arise from 
these. Such development of the leaf may be characterized as 
monstrous. It sometimes produces most beautiful crested and 
ruffled effects in the leaf. Many so-called “varieties” are based 
upon leaves that are only monstrously developed. 
Monstrous development may occur in any part of a leaf, and 
in one leaf only, or in more or in all of a plant’s leaves. When 
it occurs in more than one of a plant’s leaves, it often varies in 
degree in the different leaves, although it may affect similar parts 
in these leaves. 
When the monstrously developed leaf is fertile, monstrous 
development similar to that which appears in it often appears in 
the leaves of any plants which may spring from its spores. 
It is sometimes difficult to distinguish between monstrous de- 
velopment and normal development carried further than usual. 
The latter, however, is to be looked for in especially luxuriant, 
mature, fertile plants, and produces effects that appear the logical 
sequel to all that has gone before in the way of leaf-development; 
while the former, due to unknown causes, is often correlated with 
partial or complete sterility of the leaf, often produces freakish 
effects, and is apt to be visible from the first appearance of leaves 
on the plant. 
