42 



BIOLOGY AND HUMAN LIFE 



the center of the flower, called carpels 

 (see Fig. i8). Sometimes there is a 

 single carpel, as in the pea flower 

 {4, Fig. 197) ; sometimes there are 

 several. When there are two or more, 

 they may be quite distinct or they 

 may be more or less completely fused 

 together (Fig. 18). The carpel may 

 contain a single ovule (cherry, oak, 

 strawberry), or a few (bean, apple), 

 or very many (poppy, cucumber). 

 The name pistil (from a fancied re- 

 semblance to the pestle, with which 

 the apothecary crushes substances in 

 his mortar) is sometimes given to the 

 single carpel or to the combined car- 

 pels in a flower. The enlarged por- 

 tion, bearing the ovule or ovules, is 

 called the ovary (Fig. 17, /). The 

 upper tip of the pistil is called the 

 stigma, which means spot (Fig. 17, e). 

 Surrounding the pistil are several 

 slender stalks with knobs or enlarge- 

 ments on the ends (see d, Fig. 17). 

 These structures are called stamens, 

 from a word meaning "thready." 



Flowers differ greatly in size and 

 shape, as well as in color and odor. 

 The various parts differ in many ways 

 as we compare the flowers of different 

 species ; but the pistils and stamens 

 are always and everywhere the organs 

 that have to do with seed-making, 

 and their work is the same in all flowers. Because seeds are 

 produced only by these organs, pistils and stamens are some- 

 times spoken of as the essential organs of the flower. 



Fig. 17. Structure of a flower 



The outer set of covering leaves, 

 a, a, is called the calyx; the 

 single parts are sepals. The in- 

 ner layer, b, b, is the corolla; 

 its parts are the petals. The 

 central organ is the pistil; the 

 main body of the pistil, /, is the 

 ovary and contains one or many 

 little structures {ovules) capa- 

 ble of becoming seeds. The tip, 

 e, of the pistil is the stigma; 

 this is connected with the ovary 

 by the style c. Surrounding the 

 pistil are a number of stamens, 

 rf, consisting of a stalk, li, called 

 the filament, and an enlarged 

 capsule, g, called the anther. 

 This contains a mass of cells 

 which can be thrown out, i; 

 these cells loosened from the 

 anther are called pollen 



