THE PLANT GROUPS 133 



GAMETOPIIYTE 



Study text figures and descriptions of the megasporangium 

 of Zamia. With the aid of such descriptions study your 

 specimen with a hand lens and determine the relation of the 

 following structures : 



1. The integument layers and the micropyle. How do the 



layers of the integument differ? Is the micropyle of 

 appreciable width ? 



2. The pollen chamber and the remnant of the sporangium. 



Do you find these structures in your specimen ? How 

 are they related to the gametophyte and the arche- 

 gonial chamber ? 



3. The gametophyte. 



a. Is the gametophyte of Zamia as large as that of the 



fern ? Has it the same functions ? What was the 

 source of its food supply ? How was this in the fern ? 

 in Selaginella ? Test the gametophyte with iodine. 

 Does it contain reserve starch? 



b. Archegoma. How many archegonia are there on a 



single gametophyte of Zamia ? How do they compare 

 in structure with the archegonia of Selaginella, ferns, 

 and mosses ? Have any structures common to the 

 earlier archegonia been lost ? Note the archegonial 

 chamber. What is its special function at the time 

 of fertilization ? Draw the upper third of the mega- 

 sporangium and gametophyte to bring out the above 

 structures. Label. 



4. Pollination and fertilization. How is pollination effected 



in Zamia 1 Is self-pollination or cross-pollination the 

 rule? How does the pollen grain reach the pollen 

 chamber ? What is the function of the pollen tube ? 

 How is fertilization effected in Cycadales ? In what 



