botakical introduction 43 



The Flower. 



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

 perpetuate the species. The essential parts are tire stamens 

 aird pistil. Tlie pistil is in the centre of the liower, and 

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

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

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

 receive the pollen or male element. The stigma is frec|uently 

 supported hy a stalk termed tire style. In some flowers the 

 pistil consists of a numher of parts called carpels, each cou- 

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

 separate from each otlier, 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, tire number of compartments or cells in the ovary, or 

 the number of stigmas, affords a sufficient indication of the 

 number of carpels present. Kound the pistil the stamens a.re 

 usnall}' arranged in one or more coircentric 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, 

 fertilisation, or union, must take place between the male 

 and female elements. The pollen gram is conveyed to the 

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

 penetrates tlirough the loose tissues of tlie style into the 

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

 of the ovules, and there fertilisation takes place. After 

 fertilisation the ovule commences to develop into the seed. 



The process by which pollen is conveyed to the stigma is 

 called pollination or loosely, fertilisation. (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 



