ORCHIS TRIBE; VANILLA, SALEP 521 



length, is arrested and forms a tuber, from which the next stem 

 is shot up ; so that the plant may be said to change its place 

 every year to a considerable distance. In many instances, 

 amongst exotic species, the tuber is formed above the ground, 

 constituting what is known as the pseudo-bulb of the Orchideze ; 

 and its horizontal stem creeps along the surface as a rhizoma. In 

 these cases, the structures are more permanent, the pseudo-bulbs 

 acquiring a woody hardness, and continuing to send up stems ; 

 so that by their gradual multiplication, a large surface is often 

 covered by a single plant. 



697. It is remarkable that in a group so numerous as this, 

 consisting as it does of nearly two thousand known species, and 

 of probably as many more which, being buried in the depths of 

 unexplored tropical forests, have not yet been described, and 

 extending over almost the whole habitable globe, as far as the 

 borders of the frozen zone, there should be so few species pos- 

 sessed of properties, that make them in any way useful to Man. 

 It often happens that the most powerful virtues, or the most 

 deadly poisons, are hidden beneath a mean and insignificant 

 exterior; whilst those productions of nature which charm the 

 eye with their beauty, and delight the senses with their perfume, 

 have the least relation with the wants of mankind. So it appears 

 to be in this instance. The aromatic substance called Vanilla, 

 which is sometimes used as an ingredient in chocolate, also to 

 flavour sweet dishes, and to perfume snuff, is the succulent frwit 

 of an Orchideous plant, which, in the "West Indies, creeps over 

 trees and walls like ivy. A nutritive substance termed Salep, 

 somewhat resembling Arrow-root or Sago, is obtained from the 

 tubers of a species which grows in Turkey and Persia, where it 

 is highly esteemed. It used to be sold at the corners of the 

 streets in London, and was a favourite drink with porters, coal- 

 heavers, and other hard-working people, by whom it was consi- 

 dered very strengthening ; and the comparative disuse into which 

 it has fallen is perhaps to be regretted. It is said to contain a 

 greater amount of nutriment in the same buMf, than any othei- 

 vegetable substance ; and for this reason it is much employed by 



