io8 BOTANY 



of which still persist, we find that in the latter all the 

 structures are exposed freely ; in the former the greater 

 part are embedded deeply in other parts of the plant. 



We shall return to this subject in connection with 

 the mechanism of the flower in the higher plants. 



CHAPTER XIV 



REPRODUCTION OF FLOWERING PLANTS 

 VEGETATIVE PROPAGATION 



THE last requirement of the plant we must consider is 

 the power of reproducing its species. 



There is a good deal of variety in the ways in which 

 this is possible ; some methods consist in separating 

 certain parts of the ordinary plant body which after a 

 time grow into new plants ; in others special reproduc- 

 tive cells are produced. The first method is often 

 spoken of as vegetative propagation. The parts which 

 can be spared for it in different plants are a good deal 

 modified and have come to be considered as separate 

 organs. They include modified stems, leaves, or roots. 



We find such structures include a part which is cap- 

 able of growing some kind of bud and a store of food 

 for the nutrition of the shoot which arises from it. 



The most easily observed of the modified stems is 

 known as the tuber. This is a stem or branch which 

 grows under the ground instead of above the surface. 

 It consists of a few internodes, which become greatly 

 swollen and filled with starch and protein. The leaves 

 are only to be seen with the help of a lens; they 

 are minute scales, which never develop further. The 

 buds are in their axils and are generally several in 

 number, so that a tuber can put out several shoots, each 

 of which may grow into a new plant. The most familiar 

 instance of a tuber is afforded by the common potato. 



