216 A BOOK OF INSECTS 



increase of which is governed by other laws ; but in the 

 case of the plants with which we are now concerned, 

 flowers are the crown and climax of all effort. 



A flower consists essentially of two parts, or sets 

 of parts. If we take a buttercup, for example, we find 

 in its centre a group of small, green bodies. These 

 are the carpels, which together make up the female 

 element of the flower. Each carpel comprises a lower 

 portion called the ovary, because it contains the ovule 

 or potential seed ; and a narrower upper portion known 

 as the style, which terminates in a small receptive tip 

 called the stigma. But the carpels are rarely separate 

 from one another, or so numerous, as they are in the 

 buttercup. Usually they are more or less completely 

 united to form a single organ, the union being often so 

 intimate that the actual number of carpels present is only 

 indicated by the lobing of the stigma and the chambers 

 of the ovary. Thus, in descriptions of flowers, the 

 female element is generally referred to collectively as 

 the pistil. Surrounding the pistil in the buttercup we 

 find the male element of the flower — the numerous closely- 

 set stamens. Each consists of a stalk, called the Jilament, 

 which bears at its summit a flattened knob termed the 

 anther. Each anther is made up of two lobes joined 

 together by a kind of cross-piece, continuous with the 

 filament and called the connective; while each lobe 

 contains two cavities within which the pollen is produced. 

 When ripe, the anthers rupture, and the pollen is shed. 



In addition to these indispensable floral elements 

 there are commonly two whorls of leaf-like structures. 

 Those of the inner whorl are termed petals; they are 

 often brightly coloured, and together make up the corolla. 

 Those of the outer whorl are termed sepals ; they are 

 commonly green, and are spoken of collectively as the 



