SECTION 5.j 



ROOTS. 



33 



Section V. ROOTS. 



65. It is a property of stems to produce roots. Stems do uot spring 

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

 When perennial herbs arise from tiie ground, as they do at spriug-time, 

 they rise from subterranean stems. 



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

 the cauhcle, that is, of the initial stem of the embryo (Fig. 5-7, 81). If 

 it goes on to grow it makes a main or tap-root, as iu Fig. 37, etc. Some 

 plants keep this main root throughout 

 their whole life, and send off only 

 small side branches ; as iu the Carrot 

 and Radish : and iu various trees, like 

 ths Oak, it takes the lead of the 

 side-brauches for several years, unless 

 accidentally injured, as a strong tap- 

 root. But commonly the main root 

 divides off very soon, and is lost iu the 

 branches. Multiple primary roots now 

 and then occur, as iu the seedHng of 

 Pumpkin (Fig. 27), where a cluster 

 is formed even at the first, from the 

 root-eud of the caulicle. 



67. Secondary Roots are those 

 M'hicli arise from other jiarts of the 

 stem. Any part of the stem may 



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

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

 young stem, when placed iu favorable circumstances, — that is, wheii 

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

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

 moisture, and iherefore to bury itself iu the soil. Propagation, by division, 

 wliicli is so common and so very important iu 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 tiie ground most commonly root at the joints; so 

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

 inff ; 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. 



Fro. 81. Seedling Maple, of tiie natural size; the root well .supplietl with root-hairs, 

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

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

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