92 ; JOURNAL AND PROCEEDINGS 
In the Pteridophytes, important differences in both these 
respects occur. The gametophyte is very much reduced, 
so much so, indeed, that in some cases it is but microscopic in 
size, while even the largest are minute compared with the sporo- 
phyte. The connection between the sporophyte and gametophyte 
is only of short duration, and in the early stages of the life of the 
sporophyte. Very soon this structure takes root in the soil, and 
from that time forth carries on an independent existence, while 
the gametophyte withers away and dies. The internal structure 
of the sporophyte has also become complex, and the different sys- 
tems of tissue well differentiated. True roots also for the first time 
make their appearance. Within the group the course of evolu- 
tion appears fairly well defined. In the fern both kinds of repro- 
ductive organs are on the same gametophyte; while in the other 
divisions of the group the tendency appears to be to have the 
reproductive organs of different kinds on separate gametophytes. 
This fact would seem to indicate that there is a potential differ- 
ence in the spores. This possible differentiation of the spores 
becomes an accomplished fact in some of the members of the 
group that are closely allied to the elub mosses. In the Selagin- 
ella, and some others, there occur two kinds of spores, large and 
small ones, known respectively as macrospores and microspores. 
With the differentiation of the spores there occurs a marked 
diminution in the size of the gametophytes. The gametophyte 
from the macrospore bears the female organ, and is so reduced 
in size as not to become independent of the spore. The gameto- 
phyte from the microspore bears the male organ, the autherozoids 
from which escape and fertilize the oosphere of the female organ. 
It will thus be seen that there is a constant tendency to a decrease 
in size of the gametophyte, accompanied by a corresponding rela- 
tive increase in the size and importance of the sporophyte. The 
conjugating cells continue very similar to the corresponding cells 
of the Bryophyta. 
The conditions outlined, as found in the heterosporous 
. Pteridophytes, continue with only very slight modifications 
among the Phanerogams. The macrospore of the preceding 
plants is the equivalent to the embryo-sac in the flowering plants. 
