112 LABORATORY AND FIELD EXERCISES 



material if available. How does the leaf}- moss 



gametophyte arise ? 



2. Embryo and young sporophyte. Study stages in the 

 development of the sporophyte. What relation does 

 the old archegonium wall sustain to the growing sporo- 

 phyte ? to the mature capsule ? Draw stages in the 

 development of the sporophyte. Label sporophyte and 

 old archegonium after reading the text discussion of 

 these structures. 



LIFE HISTORY AND SEASONAL HISTORY 



1. . What are the two alternating generations of the moss, 

 and how do they differ from similar stages in Ricdo- 

 carpus ? See the life history of Ricciocarpus in the text. 



2. Write a graphical life history of the moss plant, using 



outline figures. Indicate in the history the protonema 

 and gametophyte, and stages in the development of 

 the sporophyte. 



3. Seasonal history and alternation of generations. 



a. Are the mosses annuals, biennials, or perennials in 



habit ? How do they pass the winter ? Determine 

 the main nutritive and reproductive seasonal activities 

 of common mosses. Contrast the seasonal history 

 of mosses with that of higher plants outlined in an 

 earlier part of the text. Are the alternating genera- 

 tions related to seasonal life ? If so, how ? Would 

 tli is seasonal relation be different in different mosses ? 

 Investigate this point for yourself as far as possible 

 by studies of mosses out of doors and in textbooks. 



b. Write a brief account of your findings on the above 



points and hand in with your drawings. 



