z6o 
The Ohio Naturalist. 
[Vol. V, No. 3, 
gium. The spermatozoids swim through the water and enter the 
necks of the archegonia. So far the Selaginellas are still depend- 
ent on an aquatic condition. When a spermatozoid reaches the 
egg its nucleus unites with the egg nucleus and as a result there 
is a double amount of chromation in the fertilized egg. When 
the oospore germinates its nucleus produces twice as many 
chromosomes as were present in the cells of the parent gameto- 
phytes. This conjugation or fertilization stage, therefore, rep- 
resents the second profound change in the life cycle of the plant 
and is just opposite in its results to the reduction diyision. 
The oospore is the first cell of the sporophyte generation. It 
is not discharged but begins to diyide by a transyerse wall. The 
outer cell deyelops into a suspensor while the inner giyes rise to 
the embryo proper. In other classes the embryogeny is quite 
different and there seems to be much difference in the embry- 
ogeny of different Selaginellas. In the water ferns the deyelop- 
ment of the embryo is much the same as in the homosporous 
ferns. 
The embryo is pushed down into the centre of the mass of 
food cells in the lower part of the female gametophyte by the 
rapid growth of the suspensor. It deyelops a foot, root, and 
stem tip with two small leayes called cotyledons. The foot occu- 
pies the cayity of the megaspore and takes up the food stored 
there. The root grow's out, passes down into the ground, and 
begins to take up water with dissolyed mineral salts. The stem 
with the cotyledons grows upward, deyelops chlorophyll, and 
thus begins the manufacture of food The embryo changes grad- 
ually from a phagophyte, nourished entirely by the female parent, 
to a holophyte, manufacturing its own food from the simple com- 
pounds taken from the earth and air. It also passes gradually 
from the enclosed condition to the external world, there being no 
such sudden change as the embryo undergoes during the sprout- 
ing of a seed. 
The little embryo sporophyte, having established relation- 
ships with the moist soil, air, and sunlight, continues to develop 
into a mature plant while the female gametophyte, its mother, 
dies. The gametophytes are short lived and are so reduced in 
body that their life consists mainly in accomplishing the impor- 
tant process of fertilization and in assisting the sporophyte to get 
a proper start during its early and helpless, juvenile stage. 
