234 



MORPHOLOGY. 



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

 of the inner tissue is also sterile. 



Fig. 267. 



Section of developing sporogonia of marchantia : nt, nutritive tissue of gametophyte ; st, 

 sterile tissue of sporophyte ; sj>, fertile part of sporophyte ; va, enlarged venter of arche- 

 gonium. 



493. 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. 267 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 archegonium still surrounds it. The 

 archegonium 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 gametophyte at this point of 



