BOTANICAL INTRODUCTION 43 



THE FLOWER. 



The function of the flower is to produce seed, and so to 

 perpetuate the species. The essential parts are the stamens 

 and pistil. The pistil is in the centre of the flower, and 

 contains the female organs. At its base is the seed vessel, or 

 ovary, containing the unfertilized seeds or ovules. At the tip 

 is the stigma, which is the part of the flower specialized to 

 receive the pollen or male element. The stigma is frequently 

 supported by a stalk termed the style. In some flowers the 

 pistil consists of a number of parts called carpels, each con- 

 sisting of ovary, style, and stigma. These carpels may be 

 separate from each other, or united to form a composite pistil. 

 In some cases the union is so complete, that it is difficult to 

 say of how many carpels the pistil is formed. Generally, 

 however, the number of compartments or cells in the ovary, or 

 the number of stigmas, affords a sufficient indication of the 

 number of carpels present. Bound the pistil the stamens are 

 usually arranged in one or more concentric circles. They 

 consist of a stalk known as the filament, and an enlarged tip, 

 usually yellow, the anther. Here the pollen is borne. It 

 consists of very minute yellow grains which escape by the 

 opening of the anther. Before seed can be developed, 

 fertilization, or union, must take place between the male 

 and female elements. The pollen grain is conveyed to the 

 stigma. It there grows, and puts out a long tube, which 

 penetrates through the loose tissues of the style into the 

 ovary. In the ovary, it enters the egg-cell contained in one 

 of the ovules, and^ there fertilization takes place. After 

 fertilization the ovule commences to develop into the seed. 



The process by which pollen is conveyed to the stigma is 

 called pollination or loosely, fertilization. (Throughout the 

 book we shall use the more correct term in place of the more 

 popular one). Just as the formation and structure of the leaf 

 depend to a large extent upon its adaptations to its environ- 

 ment, in respect of assimilation and transpiration, so the form 



