42 o TEXTBOOK OF BOTANY 



11. Place a young, vigorously growing plant in a battery jar 

 containing a little water. Tie a piece of cloth over the top of the 

 jar and around the plant, so that only the leaves are exposed. 

 Coat the cloth well with paraffin or vaseline so that no water can 

 evaporate from the battery jar or from the stem of the plant. 

 Weigh the whole carefully, then place it in the light. After twenty- 

 four hours, weigh it again. Explain your results. 



12. Arrange cut leaves of various plants with the lower ends of 

 their stalks in red ink. After a short time remove them and ex- 

 amine for the paths taken by the ink through the leaves. 



Chapter XVII 



1. Study several common flowers ; compare them with the 

 flowers you have already studied as to : 



a. Numbers of sepals, petals, stamens, and pistils. 



b. Whether or not any of the parts are grown together. 



c. Whether the ovary is inferior or superior. 



d. Whether the pistils are simple or compound (that is, composed of 



one or more than one macrospore leaf) . 



e. Whether the flower is regular or irregular. 

 /. Shape, size, and structure of the ovary. 



g. Length and shape of the style. 



h. Adaptation of the stigma for catching and holding pollen. 



2. What common plants have their flowers in racemes? In 

 umbels? In spikes? In heads? In panicles? 



3. Study with a hand lens the anthers of several common flowers. 

 Notice the number and shapes of the anther sacs ; the way in which 

 they open to let the pollen escape ; whether the pollen is sticky or 

 dry and powdery. Examine pollen grains of two or three different 

 flowers under the compound microscope ; draw the grains. 



4. Shake the pollen of various plants into dishes containing 

 respectively five per cent, ten per cent, and fifteen per cent cane 

 sugar solutions. Cover the dishes. After twenty -four hours 

 examine to see which grains have germinated and how germina- 

 tion came about. Draw a germinated pollen grain. 



5. Find as many as possible of the following adaptations : flowers 

 that bloom at night only ; flowers that bloom by day and close in 

 the evening; nectar-producing structures; "guides" which seem 



