. Practical botany. Botany. ROOTS 33 Pineapple family. Aerial orchids frequently possess roots of peculiar structure, covered with a papery, absorbent layer which takes up water freely when exposed to rain or dew. One air plant, the Spanish moss (^Tillandsia) (Figs. 367, 368), common in the Gulf States, has no roots, but it imbibes water freely by means of special absorbing hairs scattered over the surface of the plant. The Tillandsia is a characteristic feature of many Southern regions, often appearing as tangled, rope- like masses hanging from the trees. 33. Reproduction by means of roots. R
. Practical botany. Botany. ROOTS 33 Pineapple family. Aerial orchids frequently possess roots of peculiar structure, covered with a papery, absorbent layer which takes up water freely when exposed to rain or dew. One air plant, the Spanish moss (^Tillandsia) (Figs. 367, 368), common in the Gulf States, has no roots, but it imbibes water freely by means of special absorbing hairs scattered over the surface of the plant. The Tillandsia is a characteristic feature of many Southern regions, often appearing as tangled, rope- like masses hanging from the trees. 33. Reproduction by means of roots. Roots are often capable of producing buds which may develop into new individuals and thus serve to propagate the plant. The sweet potato is a good instance of this, each root if buried in moist sand being capable of giving rise to several new plants (Fig. 22). Roses are propa- gated by root cuttings, and some trees, such us the silver-leaved poplar (Popuhix) and the black hnust (^Buhinui), are ^eiy troublesome because of the readiness witli which young sprouts (sometimes called suckers) sprmg up from the roots. Many bad weeds, such as the field sorrel ( h'iiiii<:r} and the Canada thistle {('iri<it(in), are reproduced by roots. In case of desu-able plants that can he propagated either by pieces of root or by seeds, it is generally better to use root cuttings, as they will grow much faster. 34. Duration of life and storage of food and water in roots. It is usual to divide plants according to their duration of life into three classes: annuals, living one year or less; biennials, living two years; perennials, living more than two jears. The boundaries between these classes are not always definite;. i"ui. 22. Vegetative reproduction of tlie s^Yeet potato The pot«t( 1 was buried in moist sand and Ijegan tn sprout, that is, tci send «iut shouts from adven- titious buds at various points. Each shoot may grow into a new plant. \bout half natural size. Please note that these
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