374 
Bower . — A Criticism , and a 
In my view, the progression fro7n foliage-leaf to sporophyll , 
as seen in the development of the individual , cannot be assumed 
to illustrate the progression as regards descent. The following 
considerations will explain this statement, which is made on 
the understanding that plants now living upon the earth 
illustrate, however imperfectly, the course which evolution 
probably took. From a comparison of these we learn that 
spore-production was the first office of the sporophyte, and 
that the spore-stage has recurred constantly in the life-cycle 
during descent. As the spore-production increased (the 
increase in numbers of spores being a manifest advantage) 
the powers of the gametophyte were insufficient to supply 
the necessary nutrition and external protection. The need 
for further supply appears to have led to the intercalation 
of a vegetative phase of the sporophyte, between fertilization 
and spore-production. In the Bryophyta the external pro- 
tection and nutrition of the spores were supplied, but with 
only a minor degree of efficiency, by vegetative development 
of sterilized tissues of the lower and peripheral parts of the 
sporogonium ; there is, however, no further elaboration of form 
beyond the occasional presence of chlorophyll, containing 
expansions of the apophysis. But in vascular plants the 
foliar development appeared : as to the details of the way 
in which it first arose we are still without definite information ; 
much less do we know for certain whether the first leaves 
which appeared were sporophylls or foliage-leaves. When 
Professor Goebel writes, ‘ It can be experimentally proved that 
the sporophylls of the Leptosporangiate Ferns are modified 
leaves/ bringing this as an argument against me, he appears 
to me to assume, on ground of their priority in the ontogeny, 
that the foliage-leaves were of prior existence from the point 
of view of descent. I assert, on the other hand, that this is 
not proved, and that a good case could be made out for priority 
of the sporophyll ; in which event the conclusion would need 
to be inverted- — the foliage-leaf would be looked upon as 
a sterilized sporophyll. This would be perfectly consistent 
with the correlation demonstrated by Professor Goebel’s 
