148 LABORATORY AND FIELD EXERCISES 



b. Morphology and structure of stamens. Study the struc- 



ture and mode of dehiscence of the anther. To what 

 do the filament and anther correspond in the fern, 

 in Selaginella, and in the spruce? Draw and label 

 the parts of the stamen in terms of sporophyll and 

 sporangia. 



c. Microsporangia. Study transverse sections of anthers 



of the buttercup, mandrake, or a similar dicotyledon. 



(1) Sporogenesis. How many microsporangia are seen 



in a transverse section of a young anther ? Where 

 is the sporophyll tissue 'and how is it differen- 

 tiated ? Is there a supplying vascular bundle and 

 surrounding cortex and epidermis ? Do the spo- 

 rangia have the same general tissues as sporangia 

 of ferns and microsporangia of Selaginella, cycads, 

 and spruce ? Are there wall cells, tapetum, and 

 sporogenous cells, or spore mother cells, in each 

 microsporangiurn of an anther ? Note carefully the 

 cell structure, including cytoplasm, nucleus, and 

 chromatin, of the cells in each of these layers. 



(2) Drawing. Outline the entire section. Detail the 



cellular structure of one microsporangium, show- 

 ing the cells of the tapetum and the sporogenous 

 cells magnified. Label correctly in terms usually 

 applied to microsporophylls and microsporangia. 



(3) Spore dissemination. Study transverse sections of 



mature anthers. What changes have occurred in 

 the microsporangia during sporogenesis ? How 

 many microsporangia unite to form one anther 

 sac ? How is dehiscence provided for ? Study the 

 wall cells of the anther sacs. Is the layer beneath 

 the epidermis structurally adapted for opening 

 the anther sacs for spore dissemination ? What 



