ZAMIA FLORID ANA 1 55 



sions of its nucleus taking place. By the first cell- 

 division two cells are formed, one, the first prothal- 

 Hal cell, representing the vegetative portion of the 

 male prothallus; the second, or antheridial cell 

 (called the "antheridial initial" by some botanists), 

 divides again, forming a tube-cell and a generative 

 cell. By the division of the generative cell, the 

 stalk-cell and body-cell are formed. The division 

 of the body-cell gives rise to two sperm-mother- 

 cells, and each of these latter become transformed 

 into a motile sperm. 



Complete the following diagram of the above se- 

 quence of cell-divisions: 



Microspore 

 O 



First Proth. Anth. Cell 



Cell 



3. Mount several pollen-grains in water, and examine 

 them under the high power. Describe their shape 

 and contents. Draw. 



4. The study of the mature male prothallus, produced 

 by the formation of a pollen-tube, will be omitted 

 here. 



H. The Young Carpellate Cone: 



1. The youngest cones offered for study were collected 

 about March i. 



2. Describe the cone, and the distribution of the mega- 

 sporophylls (carpels) on its main axis, or stem. 

 Draw, natural size. 



3. Carefully dissect 1 off one of the carpels. Describe 



1 For economy of material, with large classes, excised carpels may be 

 supplied. 



