152 



MORPHOLOG y. 



develops the stalk, ana in the outer half the part which is formed from some 

 of the inner tissue is also sterile. 



Fig. 185. 



Section of developing sporogonia of marchantia ; nt, nutritive tissue of gametophyte ; si, 

 sterile tissue of sporophyte ; j/, fertile part of sporophyte ; va, enlarged venter of arche- 

 gonium. 



325. Embryo. — In the development of the embryo we can see all the way 



through this division line between the basal half, which is completely sterile, 



and the outer half, which is the fertile part. In fig. 185 we see a young 



embryo, and it is nearly circular in section although it is composed of 



numerous cells. The basal half is attached to the base of the inner surface 



of the archegonium, and at this time the arcliegonium still surrounds it. The 



arcliegonium continues to grow then as the embryo grows, and we can see 



the remains of the shrivelled neck. The portion of the embryo attached to 



the base of the archegonium is the sterile part and is called the " foot," and 



later develops the stalk. The sporogonium during all the stages of its 



development derives its nourishment from the gametoph\'te at this point of 



