POLYTRICHUM COMMUNE 89 



14. Explain the advantage of sclerenchymatous tissue 

 in the sporophyte. Describe the distribution of 

 this tissue in the seta, and explain whether or not 

 this is an added advantage. 



15. After the sporophyte of Polytrichum begins to de- 

 velop, does it grow continuously until maturity, or 

 does a period of prolonged rest intervene? Is the 

 same true with the sporophyte of the fern? 



1 6. As directed in /, 10, p. 78, diagram the life history 

 of the moss. 



17. Outline the life cycle of the moss, as described in 

 7, u, p. 78. 



H. Comparisons: 



1 . Write the following names of organs of the gameto- 

 phyte of the moss in a column, and opposite them, 

 in another column, the names of the corresponding 

 organs of the fern; thallus, rhizoid, antheridiophore, 

 archegoniophore, antheridia, sperm, archegonium, 

 egg, paraphyses. 



2. In a similar manner compare the organs of the sporo- 

 phytes of the two plants, adding the names; sto- 

 mata, foot, calyptra, columella, apophysis, sporan- 

 gium. 



3. In a third column make a list of organs of the moss 

 not found in the fern; in a fourth column, the organs 

 of a fern not found in the moss. 



4. Compare the degree of organization of the gameto- 

 phytes of the fern and the moss, as illustrated by 

 Poly podium and Polytrichum. 



5. In like manner compare the sporophytes of the two 

 classes of plants. 



6. State several reasons for regarding Polytrichum as 

 either more or less highly organized than Poly- 

 podium. 



