. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. 42 PRACTICAL COURSE IN BOTANY various points near the base of the hypocotyl and spread out in every direction, thus giving rise to the fibrous roots of grains and grasses. 38. Root hairs. — Notice the grains of sand or sawdust that cling to the rootlets of plants grown in a bedding of that kind. Examine with a lens and see if you can account for their presence. Lay the root in water on a bit of glass, hold up to the light and look for root hairs; on what part are they most
. A practical course in botany, with especial reference to its bearings on agriculture, economics, and sanitation. Botany. 42 PRACTICAL COURSE IN BOTANY various points near the base of the hypocotyl and spread out in every direction, thus giving rise to the fibrous roots of grains and grasses. 38. Root hairs. — Notice the grains of sand or sawdust that cling to the rootlets of plants grown in a bedding of that kind. Examine with a lens and see if you can account for their presence. Lay the root in water on a bit of glass, hold up to the light and look for root hairs; on what part are they most abundant ? The hairs are the chief agents in absorbing moisture from the soil. They do not last very long, but are constantly dying and being renewed in the younger and tenderer parts of — seed- the root. These are usually broken away in ling of wheat, with tearing the roots from the soil, so that it is not easy to detect the hairs except in seedlings, even with a microscope. In oat, maple, and radish seedlings they are very abundant and clearly visible to the naked eye. The amount of absorbing surface on a root is greatly increased by their presence. 39. The root cap. — Look at the tip of the root through your lens and notice the soft, transparent crescent or horseshoe- shaped mass in which it terminates. This is the root cap and serves to protect the tender parts behind it as the roots burrow their way through the soil. Being soft and yielding, it is not so likely to be in- jured by the hard substances with which it comes in contact as would be the more compact tissue of the roots. It is composed of loose cells out of which the solid root substance is being formed; the growing point of the root, g, is at the extremity of the tip just behind the cap, c (Fig. 57). The cap is very apparent in a seedling of corn, and can easily. Fig. 57. — Diagram- matic section of a root tip : a, cortex ; b, central cylinder in which the conducting vessels are situated ; c, root cap ; g
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