CHAPTER VII 

 PLANT REPRODUCTION 



All liying things tend to reproduce their kind. If they did 

 not do so, they would pass out of existence and their race would 

 become extinct. All species of plants and animals are engaged 

 in a continuous struggle for existence (Chapter XXI). Many 

 species have ceased to exist, and we know of them only by their 

 fossil remains, which we find in and on the crust of the earth. 

 The most prominent and important organs in the reproduction 

 of most of the higher plants are the flowers, although many 

 plants reproduce by means of O'ther structures. Ths flower is a 

 specmlized shoot, and the parts are specialized leaves, a?id its 

 primary function is reproduction. The shoot is very short, and 

 the parts are brought very close together. 



Reproduction. — There are two methods of reproduction : the 

 sexual and the non-sexual. In the higher plants sexual repro- 

 duction involves the two sets of sexual organs, stamens and pis- 

 tils, which may be borne on the same or on different plants, while 

 in the non-sexual or vegetative method the sexual organs are not 

 involved and there is but one parent. 



Sexual Reproduction. — In our higher plants this involves the 

 transfer of the pollen from the stamen to the stigma of the pistil 

 of another (occasionally the same) flower, the formation of a 

 pollen tube which grows throiigh the length of the style and 

 penetrates the ovule. A male nucleus (gamete) from the pollen 

 tube enters the ovule and unites with a female nucleus (gamete) 

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