109 



method, while others again employ both methods. In the 

 higher plants asexual reproduction is often brought about by 

 means of stolons and runners, as in the Potato, Strawberry, 

 and Rubus lasiocarpus. The young plants developed become 

 separated from, and independent of, their parent by the decay 

 of those portions of the stolons and runners which lie between 

 the young plants and their parent. The same thing apparently 

 often occurs in the case of root-suckers which become indepen- 

 dent by the decay of the connecting roots. Asexual reproduction 

 is also effected by means of tubers, bulbs, corms, bulbils, and 

 tuberous roots. 



Sexual reproduction in the higher plants is effected by means 

 of seeds. From the fact that two methods of reproduction occur 

 and that some plants which depend only on the asexual method, 

 and some which depend only on the sexual method, are able to 

 exist and successfully maintain themselves in different parts of 

 the earth, we should naturally infer that each method possesses 

 certain advantages. There seems to be no doubt that this is 

 the case and that, under the conditions of existence to which 

 plants are exposed in nature, at one time one method, and at 

 another time the other method, may prove most advantageous. 

 Compared with the structures by means of which asexual re- 

 production is effected, such as bulbs, corms and tubers, seeds are 

 usually smaller in size, are usually produced in larger numbers 

 and generally possess more efficient means for their wide dis- 

 tribution. In the higher plants, therefore, sexual reproduction 

 tends to result in the establishment of a large number of young 

 plants scattered at a considerable distance both from their 

 parent and from each other. To a great extent, therefore, the 

 roots of each young plant are able to develop in layers of soil 

 which have not been exhausted by the roots of its parent, and 

 each young plant is to a great extent freed from a severe com- 

 petition for its necessaries of life with other young plants of its 

 own species, which have the same needs and requirements. 



With asexual reproduction, on the other hand, it is found that 

 the young plants, although they are not so effectually separated 

 from their parent and each other, grow, at all events at first, more 

 vigorously and attain large dimensions quicker than do those 

 developed from seed. This power of vigorous growth during early 

 youth may often be of vital importance for the existence of the 

 plant, i.e. in forest areas which are covered with a heavy growth 

 of grass in which the slow-growing young seedlings of forest 

 trees are often smothered and killed, whereas strong- growing 

 root-suckers may be able to successfully establish themselves. 



