BENEDICT: NEW VARIETIES OF NEPHROLEPIS 227 
growing season may allow the accumulation of sufficient informa- 
tion to make possible a description of these forms. F urthermore, 
the forms which have been so incompletely described in the pre- 
ceding pages are worthy of a more careful and detailed study and 
description. I hope also to start spore cultures within a few weeks, 
using not only material known to be spore-fertile, but also forms 
presumably spore-sterile in the hope that apospory may result. 
There are indications that this phenomenon may occur. 
Before concluding the present consideration, there are, how- 
€ver, two or three phases of the topic to which attention should be 
directed, by way of emphasis upon the significance of the varia- 
tions which have been described. 
First, further emphasis should be laid upon the separateness of 
the forms inter se. They are entirely discrete and distinct, and 
in this respect, are in accord with the characteristics ascribed to 
mutations. The individuals of a given variety show great uni- 
formity under any given conditions of cultivations, and do not 
Pass by imperceptible differences into related varieties. The fact 
that reversion takes place does not alter the separateness of the . 
different varieties. In fact the reversions themselves furnish the 
best possible evidence of the distinctiveness and lack of continuity 
between even closely related varieties. The truth of this statement 
is established by the fact that the reversions are rarely if ever com- 
plete. A twice-pinnate variety may show some once-pinnate leaves 
and may give rise to new plants with once-pinnate leaves, but these 
once-pinnate leaves do not show a complete return to the form, 
size, etc., of the leaves of the original once-pinnate variety. The 
leaves of the reverted plant tend always to retain something of the 
character of the twice-pinnate plant. It appears then that the 
Process by which the twice-pinnate form was produced from the 
Original once-pinnate form must represent a protoplasmic change 
which is retained to some extent, even in the reversion. I cannot 
say that reversion may never be complete, but I have not yet found 
any cases where it is. This fact, however, that in any given pro- 
gressive variation, a constitutional change is effected so pronounced 
that it can rarely if ever be completely reversed, is striking evidence 
that the varieties formed by progressive variation are distinct and 
discontinuous. 
