58 BOTANICAL GAZETTE [yuLy 
great “gap” recognized as existing between bryophytes and 
pteridophytes, as the two groups would not be phylogenetically 
connected, and would have developed along very divergent lines 
from the first. It would mean that at least two independent 
sporophyte lines have appeared, the bryophyte line probably 
with an antithetic origin, and the pteridophyte line possibly with 
an homologous origin. The great prominence of the latter ling 
with its spermatophyte sequence, is correlated with the develop 
ment of a vascular system, and it would seem as though the 
evolution of an elaborate vascular system must have depended 
upon the domination of chlorophyll work. | 
Perhaps one of the strongest arguments against the poly 
phyletic origin of archegoniate plants is the constant characte 
of the archegonium. It would seem to some inconceivable that 
an organ so definite and so characteristic, and so unlike anything 
in thallophytes, could have appeared in two independent lines. 
However, the possibility of two independent appearances of such 
an organ would depend upon its origin, a subject of great obscurity: 
That it has been derived in some way from the oogonium of 
thallophytes seems hardly to be questioned, and that it is one.tl 
the results of the exchange of aquatic for terrestrial habits sees 
hardly less doubtful. That the archegonium represents a gO! 
of oogonia protected by a layer of sterile tissue seems to be# 
reasonable suggestion, and that the differentiation of this steril 
protective layer into neck and venter would follow naturally 
from the exclusive functioning of the innermost oogonium sect 
probable enough. The conditions which induced this protectio® 
of aggregated oogonia, however, could hardly be claimed ® 
leat 
algal evidence that can be presented, as in the case of the 
less sporophyte. It must be remembered, however, althou 
may be regarded as a convenient refuge for all theories 
phylogeny, that we are dealing with a structure whose origin 
very ancient. Why the alge continue to give suggestions a 
