138 TYPE STUDIES 



above, observe the development of young fern plants, or 

 sporophytes. Note the position of the small first leaf 

 rising generally through the notch of the prothallium. 

 Eemove such a young sporophyte with the attached pro- 

 thallium, wash the dirt from the root, and draw under 

 low magnification. 



1. The development of the sporophyte can best be studied from micro- 

 tome sections of material cut as described in 1, 1. Younger stages 

 show the early divisions of the egg into four regions which develop 

 respectively into a stem, root, first leaf, and large foot attaching the 

 young sporophyte to the gametophyte. Later stages will show the 

 gradual differentiation of these four regions into the organs named 

 above. The large foot brings the sporophyte into intimate physio- 

 logical relations with the gametophyte (see Principles, Fig. 279, A), 

 from which it may obtain food until able to live independently 

 by the development of a root-and-leaf system. 



Eefeebnces. Campbell, 23 ; and for a detailed study of the 

 structure and life history of Pteris aquilina, see Sedgwick 

 and Wilson, An Introduction to General Biology, 1895. 



Questions. What are the growth habits of the ferns ? Are 

 they long-lived ? What are the means of reproduction ? 

 Are there other means besides spores ? Why are the spores 

 of ferns and bryophytes comparable to one another ? Trace 

 the history of the germination of fern spores. Are the pro- 

 thallia generally long-lived ? Why are they gametophytes ? 

 Are the gametophyte and sexual organs simpler in struc- 

 ture than those of the mosses and most liverworts, and in 

 what respects ? Explain how this can be in a group (pter- 

 idophytes) higher than the bryophytes. Under what con- 

 ditions are the eggs fertilized ? What are the life habits 

 at this time ? What are the chief advances of the sporo- 

 phytes of ferns over those of bryophytes? Describe the 

 life history and distinguish between the sexual phase, gamer 

 tophyte, and the asexual phase, sporophyte. Draw and 

 arrange a series of diagrams illustrating the chief stages 

 throughout the life history, using two colored pencils to 



