260 THE TEACHING BOTANIST 



tion of the Mosses as a side and barren branch, and their 

 alternation of generations, will be emphasized. 



V. The Pteridophytes 



88. What is the structure and ecology of the Fern 



plant ? 



Does the vegetative structure agree in its general 

 composition with that already studied by you 

 in the flowering plants ? 



89. What is the structure and ecology of the pro- 



thallus stage of the Fern ? 



90. What is the structure and ecology of the Selagi- 



nella ? 



91. Prepare a synoptical essay of not over three 



hundred words, upon the Natural History of 

 Pteridophytes emphasizing their ecology. 



Materials. Any Fern with the sori in good condition will 

 do ; material may be obtained from greenhouses at any time. 

 The prothalli are very difficult to find out of doors, but are 

 easy to obtain in abundance on neglected flower-pots, walls, 

 and earth in greenhouses, particularly in badly kept ones. 

 While the general structure of the prothalli is easy to deter- 

 mine, the exact structure of archegonia, in particular, is very 

 difficult for beginners, and it may be needful to have sections 

 prepared for them. Full directions and other very valuable 

 matter on this subject will be found in Atkinson's " Biology 

 of Ferns' (see bibliography on page 137). Selaginella may 



