POLYPODIUM VULGARE 77 



9. If suitable material is at hand, study stages in the 

 germination of the spores, and draw. 



10. To which of the alternating generations does the 

 fern-plant belong? Why? 



1 1 . Into what does the spore develop ? 



THE PROTHALLUS 



F. Habitat: 



i. State the locations and conditions of growth of the 

 prothallus (also called prothallium) , (a) in artificial 

 culture; (b) in nature. 



G. Naked-eye Characters: 



1. Describe the exact size (in millimeters), color, and 

 shape of the prothallus. 



2. Is it differentiated into a dorsal and a ventral sur- 

 face ? If so, how are the two surfaces distinguished ? 



3. Describe the location and character of the rhizoids. 

 H. Microscopic Characters: 



1. Mount a prothallus in water or clearing fluid, ven- 

 tral side up, under a cover-glass. 



2. Describe the structure and contents of the cells. 



3. Describe variations in thickness. Do you find a 

 thicker central portion, or cushion? 



4. Observe the growing point in the notch. 



5. Study the location and character of the rhizoids 

 Are cross-walls present? 



/. Sexual Reproduction: 



1. Among the rhizoids find small elevations, the 

 antheridia. Describe their number and distribu- 

 tion. 



2. Nearer the notch observe the archegonia, appearing, 

 in cross-section, to be composed of four' cells, sur- 

 rounding an opening or canal. 



3. Make a drawing, at least 5 cm. in longest diameter, 



