6 Development of the Fern Leaf 
leaves and the mature leaves in consequence appear sooner than 
if the plant is weak: the first leaf, also, produced by the plant 
often portrays a more advanced stage of development and the 
height of leaf-development attained is sometimes greater. The 
leaves of a sickly plant often portray minute gradations of change. 
There is evidence which tends to show that if a plant’s vitality 
be suddenly lowered, as, for example, by an injury, the first leaf 
the plant produces afterward may portray a lower stage of de- 
velopment than the last leaf it produced before, and it may or 
may not produce additional leaves before the height of leaf- 
development previously attained in its series of leaves is again at- 
tained. But more evidence is needed on this point. The most 
striking apparent case of the kind that I have seen is the follow- 
ing: 
The series of leaves produced by a young plant of Asplenium 
ebenoides had passed the stage of leaf-development at which, in 
this species, the leaf is simple, and had reached the stage at which 
the leaf is deeply pinnatifid, when the flower-pot containing the 
plant was broken and only a little earth left on the roots. The 
plant was allowed to remain in this condition for some days 
before it was re-potted, and some of its leaves were cut off. It 
then produced simple leaves again, and then a series of leaves 
leading again to the pinnatifid stage. But as A. ebenoides is a 
hybrid, and as one of the parent species has simple leaves, the 
case can be called merely one of temporary partial reversion to 
a parent type. 
It is evident that conditions of environment can lessen or 
increase a plant’s vigor, and so indirectly lessen or increase the 
degrees of development shown by its leaves individually. Little 
