THE PLANT GKOUPS 141 



b. Crametophyte. Study the structures within a germi- 



nated microspore. Do you find the two-celled male 

 gametophyte ? the generative cell ? If possible, find 

 specimens in which the generative cell has formed 

 a stalk cell and a body cell. 



c. Comparisons. Compare the above structures with the 



male gametophyte and antheridia of Selaginella and 

 cycads. What structures have been lost ? Why are 

 the lost structures not necessary in pine or spruce ? 

 To what in the germinated microspore of Selaginella 

 do the generative cell and the stalk cell of the spruce 

 correspond ? 



d. Draw a germinated microspore and male gametophyte 



of the pine or spruce. Summarize answers to ques- 

 tions under c. 



Female gametophyte. Study median long sections of 

 megasporangia in which the female gametophyte has 

 formed. Study the section with hand lens and low 

 power, comparing it with similar sections of cycad 

 megasporangia. 



a. Megasporangium. What structures of the old megaspo- 



raugium are found in the section you are studying? 

 Are there integuments, a micropyle, and sporangial 

 tissue proper ? Do they have the same relation to 

 each other as in the cycad ? Is there a distinct 

 pollen chamber ? 



b. G-ametopliyte. Study the gametophyte tissue, the arche- 



gonia, and the gametes. What is the nature of the 

 gametophyte tissue ? What is the structure of the 

 archegonia ? Have they protective wall cells con- 

 sisting of neck and venter ? How many of the usual 

 central cells (namely, neck canal cells, ventral canal 

 cells, and gamete cells) are there ? 



