A practical course in botany : with especial reference to its bearings on agriculture, economics, and sanitation . c, root cap ; g,growing point. GERMINATION AND GROWTH 43 be seen with the naked eye, especially if a thin longitudinalsection is made. It is also well seen in the water roots of thecommon duckweed {Lemna), and on those developed by acutting of the wandering Jew, when placed in water. Arethere any hairs on the root cap ? Can you account for theirabsence ? Note. —For a minute study of the structure of roots, see 67. 40. Organs of vegetation. — The three parts, root, stem,and leaf, a
A practical course in botany : with especial reference to its bearings on agriculture, economics, and sanitation . c, root cap ; g,growing point. GERMINATION AND GROWTH 43 be seen with the naked eye, especially if a thin longitudinalsection is made. It is also well seen in the water roots of thecommon duckweed {Lemna), and on those developed by acutting of the wandering Jew, when placed in water. Arethere any hairs on the root cap ? Can you account for theirabsence ? Note. —For a minute study of the structure of roots, see 67. 40. Organs of vegetation. — The three parts, root, stem,and leaf, are called organs of vegetation in contradistinction tothe flower and fruit, which constitutethe organs of reproduction. The for-mer serve to maintain the plants indi-vidual existence, the latter to produceseed for the propagation of the species,so we find that the seed is both the be-ginning and the end of vegetable life. 41. Definitions.—Organ is a generalname for any part of a living thing,whether animal or vegetable, set apartto do a certain work, as the heart forpumping blood, or the stem and leaves. Fig. 58.—Seedlings of beanin different stages of growth :cc, cotyledons, showing theplumule and hypocotyl before of a plant for conveying and digesting germination; a, b d, and e, •^ . successive stages of advance- Sap. By function is meant the ment. At d the arch of the particular work or office that an organ ^SS£, j, .Stf Jy has to perform. erected itself. 42. Seedlings of dicotyls. The bean. — Sketch, with-out removing it, a bean seedling that has just begun to showitself above ground; what part is it that protrudes first ?Sketch in succession four or five others in different stages ofadvancement. Notice how the hypocotyl is arched whereit breaks through the soil. Does this occur in the monocotyl?examined? Do the cotyledons of the bean appear aboveground? How do they get out? Can you perceive anyadvantage in their being dragged out of the ground back-wards in th
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