POLYTRICHUM COMMUNE 75 



the stem (opposite, alternate, spiral). Are the 

 leaves sessile or petiolate? Simple or compound? 

 Is there a midrib? Veins? Compare the dorsal 

 and ventral surfaces of the leaves. Describe 

 any variations in the leaves on various parts of 

 the stem. Describe the margin of the leaf -blade 

 (i.e., entire, notched, serrate, etc.), and the shape of 

 its apex and base. 



5. Compare the form of the leaves in the same regions 

 of the male and female plants. Note especially 

 the rosette of perichsetse (modified leaves) at the 

 summit of the male plant. Compare them with 

 the foliage-leaves below them. 



6. Describe the form of the stem. Is it of uniform 

 diameter? Does it branch? Compare the stems 

 of the male and female plants. 



7. Make suitable drawings, illustrating all points 

 observed under C 1-6. 



THE SPOROPHYTE 



8. Select an archegonial plant with sporophyte (sporo- 

 gonium) attached. Distinguish the long stalk 

 or seta, bearing at its summit the spore-case, or 

 sporangium. How many millimeters long is the 

 seta? Describe its surface ; its diameter throughout ; 

 its shape in imaginary cross-section. If it is angled, 

 how many angles are there? By taking hold of 

 the seta near its attachment to the gametophyte 

 and carefully pulling, separate the sporogonium 

 from the gametophyte. State, with full reasons, 

 whether or not the tissue of the foot appears to be 

 continuous with that of the gametophyte. Does 

 anything like grafting of the sporophyte onto the 

 gametophyte take place? 



