ROOTS AKD THEIR SUNCTIOIJ-S. 41 



nently, the others dropping off when no longer of service 

 to the plant. The number and ramifications of roots are 

 naturally quite variable in different kinds of plants, as 

 ■well as in the same species growing under different con- 

 ditions, and the cultivator frequently takes advantage of 

 these variations in many of the operations which he is 

 called upon to perform. 



-"' The principal office of roots is to collect nutrients from 

 the medium by which they are surrounded, furnishing a 

 vehicle for conveying the materials collected to other 

 parts of the plant. But in many instances the roots also 

 act as a support and for securing the plant in a perma- 

 nent place or position. This function of localization, 

 however, is not general throughout the vegetable king- 

 dom, but belongs to certain groups or families, and even 

 with these it is only operative during the life of the indi- 



■ yidual plant. Collectively, all plants may be said to 

 travel or change places with each successive generation, 

 and there is a vast number which are not confined to one 

 spot for any considerable period during their lives, but 

 they are continually moving from place to place, as seen 

 in many aquatic plants floating in ponds, rivers and 

 bays in all parts of the world. There are also many 

 parasitic plants, like the common Dodders (Ouscuta), 

 which at first spring up from seed buried in the earth ; 

 but the plant soon breaks loose from the parent root, 

 then moving onward over its host, from which it obtains 

 nutriment, the older parts of the stem dying and drop- 

 ping off as the younger parts advance. Such plants may 

 be said to travel in search of victims, leaving only their 

 seeds scattered along the way, while other plants, like 

 the common Black-cap Raspberry and Trailing Black- 

 berry, leave one of their kind at each place occupied. 

 The old plant sends out a long slender shoot, several feet 

 or yards in length, and from the very tip of this, new 

 roots are emitted, and in this way a new plant is estab- 



