256 TROPICAL NATURE 



of palms or of tree-ferns. Some grow best over water, others 

 must be elevated on lofty trees and well exposed to sun and 

 air. The wonderful variety in the form, structure, and colour 

 of the flowers of orchids is well known ; but even our finest 

 collections give an inadequate idea of the numbers of these 

 plants that exist in the tropics, because a large proportion of 

 them have quite inconspicuous flowers and are not worth 

 cultivation. More than thirty years ago the number of known 

 orchids was estimated by Dr. Lindley at three thousand species, 

 in Bentham and Hooker's Genera Plantarum at five thousand, 

 and it is not improbable that they may be now nearly six 

 thousand. But whatever may be the numbers of the collected 

 and described orchids, those that still remain to be discovered 

 must be enormous. Unlike ferns, the species have a very 

 limited range, and it would require the systematic work of a 

 good botanical collector during several years to exhaust any 

 productive district say such an island as Java of its orchids. 

 It is not therefore at all improbable that this remarkable 

 group may ultimately prove to be the most numerous in 

 species of all the families of flowering plants. 



Although there is a peculiarity of habit that enables one 

 soon to detect an orchidaceous plant even when not in flower, 

 yet they vary greatly in size and aspect. Some of the small 

 creeping species are hardly larger than mosses, while the larger 

 Grammatophyllums of Borneo, which grow in the forks of trees, 

 form a mass of leafy stems ten feet long, and some of the 

 terrestrial species as the American Sobralias grow erect to 

 an equal height. The fleshy aerial roots of most species give 

 them a very peculiar aspect, as they often grow to a great 

 length in the open air, spread over the surface -of rocks, or 

 attach themselves loosely to the bark of trees, extracting 

 nourishment from the rain and from the aqueous vapour of 

 the atmosphere. Yet notwithstanding the abundance and 

 variety of orchids in the equatorial forests, they seldom 

 produce much effect by their flowers. This is due partly to 

 the very large proportion of the species having quite incon- 

 spicuous flowers ; and partly to the fact that the flowering 

 season for each kind lasts but a few weeks, while different 

 species flower almost every month in the year. It is also 

 due to the manner of growth of orchids, generally in single 



