velamen वाक्य

The velamen of an orchid is the white or gray covering of aerial roots ( when dry, and usually more green when wet as a result of the appearance of underlying photosynthetic structures ).
The velamen also serves a mechanical function, protecting the tissues in the root cortex, shielding the root from transpirational water loss, and, in many cases, adhering the plant to the substrate.
Some surprising results in studies on aerial roots of Orchids show that the'Velamen'- the white spongy envelop of the aerial roots, are actually totally water proof, preventing water loss but not allowing any water in.
There are two known species, with worldwide distribution in warm, and warm-temperate waters : " Cestum veneris " ( " Venus'girdle " ) is among the largest ctenophores up to long, and can undulate slowly or quite rapidly . " Velamen parallelum ", which is typically less than long, can move much faster in what has been described as a " darting motion ".
The corporal was described as " palla corporalis ", or " velamen dominic mens ", or " opertorium dominici corporis ", etc .; and it seems generally to have been of linen, though we hear of altar-cloths of silk, or of purple; ( a coloured miniature in the tenth-century Benedictional of St . Thelwold also seems to show a purple altar-covering ), or of cloth-of-gold.

They are characterized by round-section root with thick velamen, four-angled fleshy pseudobulbs of one internode, often basally protected by dried sheaths and with only one apical leaf ( except for " Bifrenaria steyermarkii ", which occasionally has two ), plicate ( fan-folded ) enervated leathery leaves, yet malleable and not exceedingly thick, with a pseudo-petiole of basal round section, and a basal inflorescences bearing up to ten flowers, which seldom surpass the leaves'length.