234 



MORPHOLOGY. 



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

 of the inner tissue is also sterile. 



Fig. 267. 



Section of developing sporogonia of marchantia ; >it, nutriti\-i:; tissue of gametophyte ; st, 

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

 gonium. 



493. Embryo. — In the- dcvelopniL-nt of the emhryo we can ser all the w.iv 

 through this ilivision line betwiT-n the l)asal half, which is cinnpU-trly steriU-. 

 and the outer half, which is the fertile part. In hj^. 267 we see a yuung 

 emhryo, and it is nearly circular in section although it is conip(.)sed of 

 numerous cells. The hasal half is tittached to the base of the iiURT siirlace 

 of the archet^^onium, and at this time tlie arcliei^^uiium still surr(nnids it. The 

 arche^oTiium continues to ij;niw then as tlie (.■ml>r\'o L;row>. and \\e can see 

 the remains of the shrivelled neck. TIk' |)ortion of the eml>r\-o attached to 

 the base ol the arcliei^onium is tin; sterile part and is called the " loot." and 

 later develop.-, the stalk. The sjioroi^onium durini; all the sta'^(.'S of its 

 development derives its nourishment from the gamet^iphyte at this point of 



