THE PLANT GROUPS 85 



the saclike gametangia inclosing from four to six 

 visible divisions of the contained protoplast. These 

 are the future gametes. Search for other speci- 

 mens in which eight eggs, or female gametes, are 

 rounded up inside of the gametangium membrane. 

 Find also free eggs which have been liberated, as 

 they are in nature, from the gametangium. What 

 is the structure of the female gamete ? How does 

 it compare in size with the male gamete ? Is the 

 female gamete motile ? What advantage is there 

 in the small male gametes and the large female 

 gamete ? Draw a gametangium containing devel- 

 oping gametes and a free female gamete. 



c. Fertilization. The swarming of gametes around the 



eggs may often be observed if the two gametes are 

 mounted together in sea water. The act of fertiliza- 

 tion is too difficult for observation by the beginner. 



d. Female gametangia and gametes. Observe prepared 



sections cut through female receptacles and stained. 

 Note the flask-shaped receptacles from the w T alls of 

 which the oogonia and paraphyses grow out into the 

 cavity of the conceptacle. Study different stages in 

 the formation of the female gametangia and gametes. 

 Do you find small gametangia with a single nucleus 

 and cytoplasm ? Search for other stages in which 

 there are many nuclei. Find stages in which cell 

 walls have been formed separating the cytoplasm of 

 the oogonium into eight gametes. Draw the stages 

 of the gametangium observed, illustrating different 

 stages in the formation of gametes. 



e. Male gametangia and gametes. Observe sections cut 



through male reproductive branches of Fucm. Are 

 the gametes visible within the gametangia ? How do 



