The elements of botany for The elements of botany for beginners and for schools elementsofbotany00grayuoft Year: [1887] SECTION 5.] ROOTS. 33 Section V. EOOTS. 65. It is a property of stems to produce roots. Stems do not spriug from roots iu 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 (Fig. 5-7, 81). If it goes on to grow it makes a main or tap-root, a
The elements of botany for The elements of botany for beginners and for schools elementsofbotany00grayuoft Year: [1887] SECTION 5.] ROOTS. 33 Section V. EOOTS. 65. It is a property of stems to produce roots. Stems do not spriug from roots iu 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 (Fig. 5-7, 81). If it goes on to grow it makes a main or tap-root, as in Fig. 37, etc. Some 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 tlien occur, as in the seedling of Pumpkin (Fig. 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 tliem, but tbey 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 iu favorable circumstances,—that is, when placed in the soil, or otherwise supphed with moisture and screened from the hglit. For 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 underground 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
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