78 MORPHOLOGY AND LIFE HISTORY 



showing all features of the prothallus thus far 

 observed. By the side of this figure draw an out- 

 line of the prothallus, natural size. 



4. In fresh specimens motile antherizoids or sperms 

 may be found escaping from the antheridia and 

 .swimming in the water. If these are found, observe 

 the body of the sperm and the cilia. How many 

 cilia are there? Draw. 



5. If prepared slides are supplied, study cross-sections 

 of the prothallium passing through an antheridium 

 and an archegonium. Describe accurately, noting 

 the differentiation of the archegonium into a neck, 

 containing a neck-canal, and a venter, containing 

 an oosphere or egg. 



6. Make a diagram of the section, of the same scale 

 as the drawing in 3 above, and make drawings 

 showing details of structure of the antheridia and 

 archegonia as seen in longitudinal section. 



7. To what class of reproductive bodies do the sperm 

 and egg of the fern belong? To which of the alter- 

 nating generations does the prothallus belong? 

 Why? Why is it called a thallus? 



8. Is this fern monoecious or dioecious? Explain. 



9. What structure is the starting point of the sporo- 

 phyte? 



10. Diagram the life history of the fern for three genera- 

 tions, by continuing the following diagram; letting 

 G = gametophyte; s = sperm ;e = egg;S = sporo- 

 phyte; sp = asexual spore: 



/o-r, etc. 



ii. Make a diagram to show the life cycle of the fern, 

 using arrows and words, arranged in a circle. 



