52 BOTANICAL GAZETTE [JuLy 
generations derived from oospores among thallophytes, but 
regular alternation of sexual and asexual generations is not 
definitely established. When alternation becomes definite the 
sporophyte is a recognizable structure, but that this structure 
must have been established just once or in just one way is far 
from necessary. 
It may be well to contrast the leafless and leafy sporophytes. 
In the former case the structure is never independent of the 
gametophyte, develops no lateral members, has nothing com 
parable to sporangia, and its whole tendency is to render complex 
the spore-producing region. In the latter case the sporophyte 
is dependent upon the gametophyte only in its embryonic 
stage, develops prominent lateral members, has distinct simple 
sporangia, and its whole tendency is to render complex the 
sterile or nutritive tissues. As one traces the evolution of the 
bryophyte sporogonia they give evidence of increasing com 
plexity and hence rigidity, and little promise of originating such 
a diverse tendency as that shown by the sporophyte of pterido- 
phytes. The mosses are conceded to be a highly specialized, 
and hence non-productive line, the legitimate outcome of the 
whole bryophyte tendency. Why the liverwort lines may ae 
also be regarded as highly specialized and hence non-productive 
does not seem clear. It is true that the Anthoceros forms show? 
sporophyte tendency unlike the others, and that if such a spol 
phyte should become independent and put out leaves, and if the 
continuously developing spore region should be restricted and 
broken up into simple sporangia which should associate them 
selves with the leaves, we might have something like the existing 
leafy sporophytes. But there is no evidence that these thing? 
ever happened. On the contrary, the sporophyte of Anthocero® 
would seem to be as hopelessly specialized as that of other lines. 
It is true that allthe things referred to above may have happene® 
and Anthoceros may be the nearest living suggestion of 
archetypal pteridophyte, but the case is not so clear that cae 
eyes should be shut to other possibilities. : 
If the bryophyte sporogonium is responsible for the leafy 
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