110 LABORATORY AND FIELD EXERCISES 



(3) If sections of antheridia are available, study in some 

 detail the structure of the outer protective layers 

 of the antheridium and the inner sperm mother 

 cells. Make an accurate drawing of a section of 

 an antheridium. 



b. Female heads. Observe the difference in appearance of 

 male and female heads in mosses. Dissect out 

 female heads, as for the males above, or study 

 sections cut through female heads of a moss. 



(1) Sections. If .sections are studied, note the origin of 



the archegonia from the apical meristem of the 

 rnoss stem. What is the form and structure of 

 the archegonium ? Is there an outer protective 

 layer and a central column of cells as in the 

 antheridium ? Find the egg in the basal swollen 

 part (venter) of the archegonium. Detail one or 

 more archegonia and cells of the meristem from 

 which they arise. 



(2) Dissections. If slides are not available, archegonia 



may be dissected out of female heads as for 

 antheridia above. Draw archegonia if found by 

 this method, indicating the structure of the outer 

 protective layer and of the central column of 

 cells. See the account of the structure of the 

 archegonium under Ricciocarpus and the moss 

 in the text. 



(3) Comparisons. Compare the archegonium of the moss 



and the oogonium (gametangium) of algte. How 

 do they differ ? In what respects is the arche- 

 gonium better adapted for insuring fertilization 

 in land plants than the simple gainetangia of 

 the algae ? 



