174 LABORATORY AND FIELD EXERCISES 



setting seed in the summer and autumn as in the 

 spring? Be able to explain this point. 



2. Seasonal life. 



a. Compare the seasonal life of violets and buttercups. 



What are the principal activities of the violet plant 

 in spring, autumn, summer, and winter ? What por- 

 tions of the plant are active at each season? Consult 

 the text, Part I, on seasonal life. 



b. Summarize the above facts relating to the seasonal 



history of violets. 



3. Reproduction. The flower and its modifications for secur- 



ing pollination. 



a. Study the parts of the flower and their modifications. 



What modifications do you find in the perianth and 

 the essential organs ? Remove the parts of the peri- 

 anth and observe their form and structure. Note 

 the relation of the stamens to the perianth and 

 to the pistil. 



b. Cut a transverse section across a flower in the region of 



the ovary. Study the section and construct a ground 

 plan of the violet flower which will show the relation 

 of the parts of the perianth and the essential organs. 



c. Pistil and stamens. 



(1) Dissect away all of the petals except the lower one 



with the spurlike nectary. Examine the stigma 

 and anthers with a hand lens. Where is the stig- 

 matic surface ? How is it related to the anthers 

 and to the canal leading to the nectary ? Where 

 is the pollen shed ? 



(2) Bisect a flower longitudinally and study the above 



relation of pistil, stigma, and anthers to the nec- 

 tary and the lower petal. Consult Fig. 253 of 

 text and the discussion on pollination. 



