684 FAMILIES OF ANGIOSPERMS. 



The fruit. What parts of the flower are united in the fruit? Describe 

 the fruit. What is such a fruit called ? How are the seeds freed ? What 

 is the difference between a fruit and a seed in the pea plant? 



The clover (Trifolium). If it is desired to study a clover, study one 

 in a similar way. 



Nitrogen gatherers. The pea, clovers, etc., are sometimes called nitro- 

 gen gatherers (see Chapter IX). During an excursion let the pupils dig up 

 different leguminous plants, like the pea, clover, lupine, etc., and search 



Fig. 573- 

 Spray of leaves and flowers of the sugar-maple.- 



for the "tubercles" on their roots, comparing the form of the tubercles 

 on the different kinds of plants. 



Pollination. If the flowers of Cytisus from a conservatory are at hand, 

 attempt to press the point of a pencil in between the parts of the keel in 

 the case of flowers where these parts are still closed; describe the action 

 of the stamens in throwing the pollen. How could cross-pollination be 

 brought about in such a flower by the visits of insects? 



Study the common lupine (Lupinus perennis) in the same way. Study 

 the pea flower with the same object in view; has the pea flower become 

 adapted to self-pollination? 



Material. Sprays of leaves and flowers; fruit. Material can usually 

 be obtained fresh early in the spring and for some time later. 



