THE SPRING FLORA 177 



LEGUMINOSAE 



See Pollination devices in papilionaceous flowers in Part I 

 of the text, and the seasonal history of the bean and the white 

 sweet clover. See also previous laboratory work and drawings 

 011 the locust and sweet pea. Study the distinctive recognition 

 characters of representative species of Leguminosae in the field 

 and be able to summarize them under the following headings : 



1. Habit. 



a. Stems. Are the stems all herbaceous in character or 

 are there some common trees and shrubs belonging 

 to the family ? 



./>. Leaves. What are the distinctive structural and physio- 

 logical features of the leaves of all Leguminosae 

 which distinguish them from other families of plants 

 with which you are familiar ? Study the leaves of 

 several species and their reactions to light. Are 

 they simple or compound ? Have they special motor 

 organs ? 



c. Roots. Dig up the root system of the common red 

 clover, of the pea, or of the bean. Do you find en- 

 largements on various parts of the root system in the 

 form of nodules? These nodules contain the nitrogen- 

 gathering bacteria which enable these plants to use 

 free nitrogen from the soil. Observe also the extent 

 of the root system as compared with the leaf system. 

 Is the root surface exposed to the air ? 



2. Reproduction. 

 a. Flowers. 



(1) Structure. Have the'flowers of the family a common 

 structure, floral plan, and form ? Note any floral 

 modifications from the usual type of the flowers 

 of the family illustrated in the text. 



