CHAPTER XII 



THE BEAN 



161. Angiosperms: the Bean Plant. — The great majority 

 of seed plants, unlike the pine, are angiosperms ; they produce 

 their o\niles (macrospore sacs) , and consequently their seeds, 

 inside a closed vessel which is called 

 an oi'ary. When the ovules develop 

 into seeds, the ovar\- becomes a fruit. 

 Almost all our cultivated plants are 

 angiosperms ; so also are most forest 

 trees (apart from the cone-bearing 

 ones) and most other conspicuous 

 wild plants except the mosses and 

 ferns. In stud},Tng the cucumber we 

 have learned something of the struc- 

 ture and way of life of an angio- 

 sperm, and the bean is a convenient 

 plant to use for a fuller study. Any 

 of the numerous cultivated varieties 

 of bean will answer for this purpose. 

 Like the cucumber, the bean is an 

 annual ; that is, none of its parts live 



through the winter and grow from year to year, as the trunk 

 and roots of the pine do. Some varieties are low or " bush " 

 beans; some are climbing or ' pole " beans. The stem of 

 a climbing bean coils about any slender object that it 

 touches, such as a pole, or the stem or branch of another 

 plant (Fig. 80). This coiling is due to an unequal growth 

 of the stem on its different sides, which causes the upper 



137 



Fig. 80. — Portion of a 

 bean stem twining about 

 a support. 



