File:The natural history of plants, their forms, growth, reproduction, and distribution; (1902) (14781073064).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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A double function appertains to the roots of these Orchideee which inhabittrees. On the one hand they have to fix the entire orchid-plant to the bark, and,on the other, to supply it with nutriment. When the growing tip of an orchidsroot comes into contact with a solid body, it adheres closely to it, flatucns out moreor less, sometimes even becoming strap-shaped (see fig. 15), and develops papilli-form or tubular cells, which grow into organic union with the substratum, andmight conveniently be termed clamp-cells. In many cases these cells creep overthe bark, divide, interlace, and form regular wefts. The organic connection withthe substratum is so intimate that an attempt to separate the two usually results ABSORPTION OF WATER BY EPIPHYTES. 221 in a detachment of the most superficial parts of the bark, but not of the tubularcells. Now, if a root, after having sent out cells of this kind which contract anorganic union with the substratum, reaches into the open, beyond the limit of the
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Fig. 50.—Aerial Roots of an Orcliid epiphytic upon the bark of the branili of a tree. substratum, it immediately ceases to develop clamp-cells, loses its ligulate shape,and hangs down from the tree in the form of a sinuous white filament. A fewroot-fibres are as a rule sufficient to fix the plant to its substratum, the bark of thetree, and the rest of the roots put forth by the orchid grow from beginning to end, 222 ABSORPTION OF WATER BY EPIPHYTES. freely in the air. The^^ are not infrequently to be seen crowded together in greatnumbers at the base of the plant, fox-ming regular tassels suspended from the darkbark of the branches as may be seen in fig. 50, where an Oncidium is represented. Each of these aerial roots is invested externally by a white membranous orpapery envelope, and it is the cells of this covering that own the resemblance, abovereferred to, to the cells of Leucohryuvi and Bog-mosses. Their walls are furnishedwith narrow, projecting spiral thickenings and therefore

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