264 Bower.— Imperfect Sporangia in certain 
logy of a family of Flowering Plants. And just as the honey- 
leaves may be altered stamens, so may the foliage -leaves of 
Lycopods be sterilized sporophylls. 
But, conversely, we may turn for analogy to the Bryophyta. 
A comparative treatment of the sporogonium illustrates the 
progressive sterilization and intercalation of a vegetative 
phase between fertilization and spore-production. In the 
above pages the analogy has been pointed out between the 
balance of vegetative and reproductive phases in the sporo- 
gonium of certain Mosses and that in the Lycopods ; and 
how in both series it may be recognized that there is a repro- 
ductive zone characterized at its lower limit by structural 
evidences of evanescent spore-development, and at its upper 
limit by evidences of nascent spore-production ; in both 
regions the development being incomplete. The idea is thus 
presented of a fertile phase in the individual, which may in 
the descent move on to later phases in the individual, pro- 
gressive sterilization taking place below, and progressive 
apical growth extending the plant above ; with the result of 
an increasing vegetative system for nutrition. This analogy 
in the two large series should be allowed due comparative 
weight, and not discounted on the mere ground that the 
Bryophyta have a concrete archesporium and no appendages, 
while the Lycopods are leafy and bear separate sporangia. 
The lines of descent have probably been quite distinct ; but 
the demands of nutrition, which dominated both, were alike. 
The endeavour must be made to preserve a consistent 
morphological method for the Pteridophyta and for other 
plants both higher and lower in the scale. And to this end, 
just as much prominence should be given to the abortive 
parts which are present in the Pteridophyta, and especially in 
the simple Lycopods, as to the abortive parts in the Angio- 
spermic flower : and they should be open to the same inter- 
pretation. On the other hand, the progressive sterilization 
admitted as an important factor in the progress of the Bryo- 
phyte sporogonium should equally be admitted, where the 
facts indicate it, in the upward progress of the Pteridophyta. 
