THE HAMILTON ASSOCIATION 91 
of them, there are found organs of reproduction that have reach- 
ed a fairly high degree of perfection, the two conjugating cells 
being well differentiated. 
In those fungi which are structurally most complex, no 
organs of reproduction have so far been observed, and conse- 
quently the pathway of their evolution has been lost. The 
absence of reproductive organs is most probably due to a process 
of degeneration that has resulted in the entire disappearance of 
these organs, and the plants have reverted to the more primitive 
mode, namely, asexual reproduction. 
Leaving the Algewe and Fungi, the plants next in the ascending 
scale are those included in the Bryophyta. In these plants the 
organs of reproduction are highly specialized. The conjugating 
cells are of two kinds, a non-motile one, which does not become 
detached from the parent plant, and a motile one, which becomes 
detached and moves about readily. We have also in these plants, 
for the first time, an alternation of generations. The gameto- 
phyte generation is the larger and more important, while the 
sporophyte generation is very much smaller, and in some cases 
not observable except with a magnifying glass. Within the 
croup Bryophyta the evolution appears to have taken place along 
the line from the very small sporophyte, on a relatively large 
gametophyte, to a much larger sporophyte on a relatively smaller 
cametophyte. 
It is also worthy of note that the sporophyte never becomes 
independent of the gametophyte, consequently the former de 
pends upon the latter for its nourishment. 
The Pteridophytes, including the ferns, equisetums, club- 
mosses and allied plants, have a reproductive system similar in 
a general way to that of the Bryophyta. Nevertheless, there are 
some very important respects in which these plants are an ad- 
vance upon the mosses. Referring again to the Bryophyta, it 
will be recalled that the gametophyte is the more important 
generation of the two, and that the sporophyte never exists except 
in connection with the gametophyte. 
