File:The natural history of plants, their forms, growth, reproduction, and distribution; (1902) (14803285893).jpg

Identifier: naturalhistoryof01kern (find matches)
Title: The natural history of plants, their forms, growth, reproduction, and distribution;
Year: 1902 (1900s)
Authors: Kerner von Marilaun, Anton, 1831-1898 Oliver, Francis Wall, 1864- Macdonald, Mary Frances Ewart Busk, Marian Balfour, Lady
Subjects: Botany
Publisher: London, Blackie
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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t is true, when theyare treated like land-plants and planted in soil; but a few species, on occasion, burytheir aerial roots spontaneously in the earth and push off their envelopes, and thenthe imbedded parts exercise the same functions as in the case of land-plants. We have already mentioned that, in addition to thousands of orchids, severalAroidese exhibit the porous, papery covering on their aerial roots. But still morefrequently the air-roots of Aroids, which live as epiphytes upon trees, are furnishedwith a dense fringe of so-called root-hairs in a broad zone behind the growing-point. The hairs project on all sides from the roots, which are surrounded by air;they are crowded very closely together and give the parts affected a velvetyappearance. Besides several Aroidese, one of which (Philodendron Lindeni) isdrawn on the left side of fig. 51, many other epiphytes, such as the South 224 ABSORPTION OF WATER BY EPIPHYTES. 7- 7 ...-^ belono-ino-to the Commelynacese, represented on the
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w w\ y IV il.-AH 1.1 K- 1. ill, „..t I, ,1,,, on the let. Philodmdro,. Lmdtnl. <,n llie rlgln c««p.l.» 2»~i«. coating on their aerial roots. The roots o£ the tree-ferns are short but spring inthou^atds from the thick stem, and are so closely packed that - ™ho e surfacclothed as it were by a woven mantle of rootlets. After some tone these aeruaroots turn deep brown, whilst the hairs collapse and die, and both are converted ABSORPTION OF RAIN AND DEW BY THE FOLIAGE-LEAVES. 225 into a mouldering mass. But as soon as they perish other new air-roots, coveredwith golden-brown velvet, make their appearance and take their place. These aerialroots never reach the ground or adhere to any substratum, so that their hairscannot contract an organic connection with a solid body. It is consequently alsoimpossible in this case for the root-hairs to draw moisture from the soil in thecapacity of absorption-cells. These root-hairs, however, are scarcely ever in a position to take up even the

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