50 TROPICAL NATURE, AND OTHER ESSAYS. 



forks or on the branches of trees ; they abound on fallen 

 trunks ; they spread over rocks, or hang down the face 

 of precipices ; while some, like our northern species, 

 grow on the ground among grass and herbage. Some 

 trees whose bark is especially well adapted for their 

 support are crowded with them, and these form natural 

 orchid-gardens. Some orchids are particularly fond of 

 the decaying leaf-stalks 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 3,000 

 species, and it is not improbable that they may be now* 

 nearly doubled. 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 there- 

 fore 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 



