SECTION 5.] 



BOOTS. 



33 



Section V. ROOTS. 



65. It is a property of stems to produce roots. Stems do not spring 

 from roots in ordinary cases, as is generally thought, but roots from stems. 

 When perennial herbs arise from the ground, as they do at spring-time, 

 they rise from subterranean stems. 



66. The Primary Root is a downward growth from the root-end of 

 • the caulicle, that is, of the initial stem of the embryo (Pig. 5-7, 81). If 



it goes on to grow it makes a main or tap-root, as in Kg. 37, etc. Soma 



plants keep this main root throughout 



their whole life, and send off only 



small side branches ; as in the Carrot 



and Radish : and in various trees, like 



the Oak, it takes the lead of the 



side-branches for several years, unless 



accidentally injured, as a strong tap 



root. But commonly the main root 



divides off very soon, and is lost in the 



branches. Multiple primary roots now 



and flien occur, as in the seedling of 



Pumpkin (Pig. 27), where a cluster ■ 



is formed even at the first, from the 



root-end of the caulicle. 



67. Secondary Roots are those 

 which arise from other parts of the 

 stem. Any part of the stem may 



produce them, but they most readily come from the nodes. As a general 

 rule they naturally spring, or may be made to spring, from almost any 

 young stem, when placed in favorable circumstances, —that is, when 

 placed in the soil, or otherwise supplied with moisture and screened from 

 the light. Por the special tendency of the root is to avoid the light, seek 

 moisture, and therefore to bury itself in the soil. Propagation by division, 

 which is so common and so very important in cultivation, depends upon 

 the proclivity of stems to strike root. Stems or branches which remain 

 under ground give out roots as freely as roots themselves give off branches. 

 Stems which creep on the ground most commonly root at the joints ; so 

 will most branches when bent to the ground, as in propagation by layer- 

 ing; and propagation by cuttings equally depends upon the tendency of the 

 cut end of a shoot to produce roots. Thus, a piece of a plant which has 

 stem and leaves, either developed or in the bud, may be made to produce 

 roots, and so become an independent plant. 



FlO. 81. Seedling Maple, of the natural size ; the root well supplied with root-hairs, 

 here large enough to be seen by the naked eye. 82. Lower end of this root,magni. 

 fled, the root seen just as root-hairs are beginning to form a little behind the tip. 



