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. 



