76 



APPLIED BIOLOGY 



water. The significance of these details of structure will be made 

 clear in the next part of this chapter, in which the work of the leaf 

 is described. 



THE REPRODUCTION OF THE BEAN PLANT 



The Bean Flower 



74. Simple Flowers. The bean flower is too difficult for the 

 first examination of the parts of a flower. However, the parts of 

 simple flowers are usually so well learned in the nature-study of 

 the elementary schools that it is really an advantage to study in 

 the high school different types of flowers. In case any pupils in 

 the class have not previously learned the parts of any simple 

 flower, they should first study one, identifying : (1) The calyx, 

 composed of sepals; (2) corolla, composed of petals; (3) stamens, 

 composed of the stalk or filament and the anther, bearing minute 

 grains of pollen ; (4) in the center of the flowers the pistil, composed 

 of the ovary, and the style, which extends upward and has the 

 stigma at its end. Flowers which have separate petals (scillas, 

 tulips, sedum, lilies, etc.) are good for such pre- 

 liminary study of the parts of simple flowers. 



75. Study of Bean Flower. (L) Bean plants 

 six to ten weeks old will furnish all the stages 

 needed for this study. Note how the flower- 

 stalks (pedicels) are attached at the nodes of 

 the stem and often in the axils of the leaf ; that 

 is, in the angle between leaf and stem. Iden- 

 tify : (1) two green leaf -like structures (bracts) 

 at the base of the flower. On very young 

 flower buds on the same plant these bracts may 

 be seen inclosing the flower. (2) Between the 

 bracts and the corolla is the calyx, composed of 

 five sepals united into a cup. This can be seen 

 best in an old flower from which the corolla is 

 ready to fall. (3) The petals (white, pink, or 

 red) of the corolla, five in number and unequal 

 in size, are arranged as in the diagram in Fig. 

 31. The three largest petals are so prominent 

 that at first sight the flower appears to have 

 only three ; but two smaller petals are united and coiled so as to lie 

 between the three largest petals. The largest petal of a flower like 



FIG. 31. Pea flower. 

 , " standard " ; w, 

 "wings"; k, "keel"; 

 see text. (From 

 Gray.) 



