POLYTRICHUM COMMUNE 83 



an end view of the sporangium with the operculum 

 removed. Make a drawing of the operculum, 

 also 30 mm. in diameter. 



18. With the razor carefully make a longitudinal section 

 of the capsule, just to one side of its central axis. 

 Observe the wall of the sporangium; a central 

 organ (columella) ; and, between the two, a mass 

 of spores. 



19. Describe the structural relation of the columella 

 to the epiphragm. What, in reality, is the latter? 



20. Describe the relative number, color and attach- 

 ment or non-attachment of the spores, so far as 

 may be ascertained without the aid of the micro- 

 scope. 



21. Make a drawing, ten times natural size, illustrating 

 everything observed under 18-20. 



2 2 . From the above observations construct a diagram of 

 an imaginary cross-section of the sporangium near 

 the middle. Compare the diagram with an actual 

 cross-section. 



23. Carefully preserve the sporophyte in a covered 

 watch-glass or other convenient nioist (not wet) 

 place until the next laboratory period, or proceed at 

 once with the following observations (D): 



D, Microscopic Characters: 



THE SPOROPHYTE 



1. With a sharp scalpel remove a thin piece from the 

 base of the sporangium, cutting parallel to the sur- 

 face, and mount it in water with the outer surface 

 uppermost. 



2. Examine the mounted tissue under the low, then 

 under the high power, to see if stomata are present. 



