2 6o The Ohio Naturalist. [Vol. V, No. 3, 



gitim. 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 division. 



The oospore is the first cell of the sporophyte generation. It 

 is not discharged but begins to divide by a transverse wall. The 

 outer cell develops into a suspensor while the inner gives 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 develop- 

 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 develops a foot, root, and 

 stem tip with two small leaves called cotyledons. The foot occu- 

 pies the cavity of the megaspore and takes up the food stored 

 there. The root grows out, passes down into the ground, and 

 begins to take up water with dissolved mineral salts. The stem 

 with the cotyledons grows upward, develops chlorophyll, and 

 thus begins the manufacture of fond. 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 gametophvte, 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. 



