152 GROWTH AND WORK OF PLANTS 



250. The pistil is simple. The ovary is flattened, elongate, 

 with the ovules arranged in a row at the upper edge. It forms 

 the pod, or legume. The style is slender and curved upward, 

 and bears the stigma, which is narrowly elliptical and somewhat 

 broader than the style. The free part of the filaments are curved 

 also to surround the style, bringing the anthers close around the 

 stigma, upon which the pollen is shed before the flower opens, so 

 that self-pollination usually takes place. 



251. This type of flower, called papilionaceous because of 

 its resemblance to a butterfly (papilio), is characteristic of a large 

 number of plants belonging to the important family known as 



Fig. 113- 



Flowers of sweet pea, corolla removed. Note diadelphous stamens, one single one, 

 the others all united. 



the pulse family or pea family (Leguminosa, sometimes called 

 Papilionacea), including the peas, beans, clovers, alfalfa, etc. 

 Besides their importance as food for man and animals, they play 

 a very important part in the enrichment of the soil in nitrogen 

 through the nitrogen-fixing bacteria which grow as parasites in 

 their roots. 



