The American Botanist, 1902, Vol. 3

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Excerpt from The American Botanist, 1902, Vol. 3: Devoted to Economic and Ecological BotanyThe roots of epiphytal Orchids differ from those of terrestrial plants is being covered with a white papery substance, called the velamen, and the cells of the velamen serve the double purpose of condensing or absorbing aqueous vapour from the atmosphere, when any is present, and of protecting the underlying cells from excessive evaporation during periods of drought. In its absorp tive character it is analagous with the outer cells of the bog-mosses (sphagnum) and L'eucobrjmm, where the small chlorophyll-bear ing cells are covered by large colourless cells, having very thin walls, which are variously perforated, and not only absorb water in liquid state, like a sponge, but also have the power of condens ing it when in the form of vapour. A double function appertains to the roots of epiphytal Orchids, firstly to fix the plant to the bark and secondly to supply it with nutriment. When the tip of a root comes in contact with a solid body it adheres closely to it, ¿attens itself out more or less, develops papilliform or tubular cells, which grow into organic union with the substratum, and act as holdfasts. But if the root extends beyond the limit of the substratum it ceases to develop these clamp - cells, and hangs down in the form of a white filament. Many o-f these aerial roots do not become attach ed at all but hang freely in the air, often forming regular tassels.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.