THE PLANT GROUPS 79 



c. Fertilization. 



(1) Observe stages in which gametes are fusing to form 



zygotes. What is the difference in the behav- 

 ior of the two gametes during fertilization ? On 

 what basis can one be designated as male and 

 the other as female ? 



(2) Draw stages in fertilization as observed. 



d. The zygote. 



(1) Study cells in which zygotes are formed. What is 

 the structure of the zygote cell ? Distinguish 

 between pyrenoids and nuclei in the zygote cell. 

 Stain zygotes with iodine. What kind of reserve 

 food does the zygote contain ? When and for 

 what purpose will this food be used ? Draw 

 two or three zygotes to illustrate their cell 

 structure. 



4. Life history of Spirogyra and Protococcus. Construct a 

 graphical life history of Spirogyra. Is it possible to 

 construct a similar graphical history for Protococcus ? 

 In what fundamental respects does the life history of 

 Spirogyra differ from that of Protococcus ? 



VMTHERIA (GREEX FELT) 



Select fruiting specimens of some species of VaucJieria for 

 study. Observe the following points regarding its habitat, habit, 

 and structure : 



1. Habit. In what respect is Vaucheria peculiar in its gen- 

 eral structure ? Is it a simple or a branched filament ? 

 Is the plant body differentiated into root and shoot ? 

 What is its general microscopic structure ? Is it uni- 

 cellular or multicellular ? What kind of chloroplasts 

 has it? 



