DENDROBIUM. 7 



importance, are purposely omitted, with the exception of six of the 

 best known. With respect to the species found in northern India 

 and Assam, their habitats have been so vaguely reported — in nearly 

 every case simply Nepaul, Assam, etc. — that their geographical position 

 as indicated on the map, may by no means be the precise one they 

 should there occupy ; nor do they probably occur in the somewhat 

 formal sequence as regards locality in which their names have been 

 necessarily placed. Moreover, the existing confusion in the ortho- 

 graphy of Indian names has made it impossible to determine, on 

 modern maps, the localities of many species given by the older 

 botanists. Widely distributed species, as aureum, crumenatum, for- 

 mosum, secundum, etc., are inserted more than once, but always in 

 localities in which they are known to occur. The few species reported 

 from New Guinea are assumed to have been found in the best known 

 or Dutch division of the island, except those recently gathered on the 

 Owen Stanley range of mountains in the extreme south-east. The 

 names of many Dendrobes of botanical interest only are inserted 

 because their habitats are well authenticated ; this is especially the 

 case with the Australian species, the majority of which occur in an 

 almost uninterrupted belt along the east coast. The names of a few 

 species prized by amateurs are omitted on account of the total absence 

 of reliable information respecting their habitats, or because their 

 native countries lie without the range of the maps. 



The climate of the Dendrobiuni region is characterised by a high 

 average temperature, accompanied with great moisture throughout the 

 greater part of the year, the Australian portion of it being a partial 

 exception that will be presently noted. In the lower Himalayan zone 

 the temperature ranges from 27° — 33° C. (80° — 90° F.), and even 

 higher in the enclosed valleys, while the sun is at and near the 

 summer solstice ; but at the opposite season it is from 6° — 9° C. 

 (10° — 15° F.) lower. The humidity of the atmosphere during the 

 greater part of the year is near the saturation point, owing to the 

 enormous amount of vapour which ascends from the Bay of Bengal being 

 drifted towards the mountains, and which, being condensed by contact 

 with the higher and colder zone, is precipitated as rain into the lower 

 valleys. This precipitation increases in amount in proceeding east- 

 wards to the Khasia Hills, where it attains a maximum, as much as 

 600 inches having been registered in one year, and of this enormous 

 quantity a fall of 250 inches of rain has been known in one month 

 (August).* This excessive fall is, however, quite local. A.t Sylhet, 

 * Hooker's Himalayan Journals, II. p. 283. 



