122 • TYPE STUDIES 



various stages of development. Observe their arrange- 

 ment in lines between fringes. Where are the oldest 

 sporophytes situated ? 



3. Make sections in pith across rather young or medium- 

 sized receptacles. Some of them will show the flask- 

 shaped archegonia of various ages. Note the swollen base, 

 or venter, and the neck. If the archegonium be not fully 

 mature, a line of canal cells is to be seen in the neck, ter- 

 minating in the large egg within the swollen base. Illus- 

 trate these points in figures. 



4. Hunt for older stages following the opening of the neck 

 and fertilization of the Qg%. Note the shriveled neck and 

 much enlarged base, which now contains a developing 

 sporophyte. The older fertilized archegonia become sur- 

 roimded by an open, sac-like envelope (perianth) which 

 develops at their base. 



5. Make sections of the stalk and examine under m.p., noting the two 

 grooves containing rhizoids. Follow these grooves up and down on 

 the stalk, and trace them to the point where the stalk joins the 

 thallus. What is the significance of the rhizoids in the grooves? 

 What relation does the stalk bear to the thallus ? 



6. Microtome sections of the archegonial receptacles (Sec. 212) are al- 

 most essential to an understanding of the development and arrange- 

 ment of the archegonia and their minute structure. They also show 

 stages in the development of the sporophyte. 



F. The sporophyte. Section old archegonial receptacles. Also 

 pick off some of the sporophytes which have opened and are 

 discharging spores, and mount them entire. Note and show 

 in drawings : 



1. That the mature sporophyte consists of ^ spore case borne 

 on a stalk attached by a/oof to the base of the archegonium. 

 The latter has been ruptured by the development of the 

 sporophyte. 



2. That the spore case at maturity opens and discharges the 

 spores which lie among a tangle of spirally marked fila- 

 ments called elaters. 



