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1899] ORIGIN OF THE LEAFY SPOROPHYTE 59 
the origin of the bryophyte sporogonium, and, so far as known, 
give no intimation of the independent origin of the leafy sporo- 
phyte, isa pertinent question. It seems to be also true, how- 
ever, that the bryophytes give no clear suggestions as to the 
origin of the leafy sporophyte, and we are left to imagine the 
method of its origin from either group. 
In thinking of this possible disconnection of the bryophyte 
and pteridophyte lines, it may be well to recall the similar 
experience of the gymnosperm and angiosperm lines. Certainly 
the gymnosperms and angiosperms seem to have more characters 
in common than do the bryophytes and pteridophytes, and seem 
to be more insistent in their demand for a common phylogeny ; 
yet that the gymnosperms represent at least one independent 
phylum can hardly be longer doubted. 
All such discussion is, of course, very vague and general, 
and may not commend itself to many as profitable. But it 
Serves its purpose in stating the problem, and in presenting the 
possible alternative solutions. We have been in danger of 
restricting the operations of evolution too rigidly, making the 
lines of advance too few, and forgetting the possibilities of 
change during the enormous stretches of time. The polyphyletic 
origin of similar structures and of similar groups makes the 
Problems of phylogeny immensely more complex, but is probably 
much more consistent with the facts. 
THE UNIVERSITY oF CHICAGO. 
