262 Bower. — Imperfect Sporangia in certain 
that the strobili are, when defined, similar in their broad 
characters to those of modern times, showing diminution of 
sporangia at the apex, and also at the base. Though there is 
thus little conclusive evidence from such facts as have been 
brought forward relating to fossils, at least we may assert that, 
so far as it goes, it does not run counter to the results that 
have been obtained by" comparison of living plants. 
General Conclusion. 
Abortive parts are not such prominent features in plants as 
in animals, and they have played a less important role in the 
theories of vegetable morphology than in those of comparative 
zoology. This is probably to be understood as a consequence 
of the continued embryology of plants, and the unlimited 
number of the appendicular parts, arising from their persistent 
meristems. Thus the initiation of individual parts, such as 
the reproductive organs of the sporophyte, may be deferred 
so late as to remove them far from the initial embryology of 
the plant. In animals, on the other hand,' it is frequently the 
parts initiated early in the embryology which supply the best 
examples of vestigial organs. 
But in the above pages we have seen that incompletely 
developed parts are frequent among the Pteridophyta. Such 
recurrent phenomena must not be ignored. Their treatment 
should be consistent with that of similar phenomena in other 
groups of plants, or in animals. And naturally we turn to 
the Phanerogams for guidance in morphological method, since 
in their comparative treatment abortive parts have been taken 
fully into account. It will be unnecessary to quote special 
instances of this, for the recognition of certain abortive parts 
as vestigial — that is representing parts which in the ancestry 
were once actually functional — is a common position in floral 
morphology. The ready acceptance of such conclusions for 
Flowering Plants is probably due to the fact that, in many 
cases, closely related genera and species allow of a complete 
and consecutive train of comparison, while also the arguments 
have for the most part dealt only with the parts of the flower, 
