250. MR. Е. F. IM THURN ON THE PLANTS 
Probably no district of equally small size, after such brief and cursory exploration, has 
yielded greater, or as great, botanical results as has Roraima; still more probable is it 
that few small districts are so distinctly marked off from the country immediately sur- 
rounding them by such great and remarkable peculiarities in their vegetation. In brief, 
the district of Roraima is, from a botanical point of view, chiefly interesting as an oasis 
clothed with a vegetation distinct from that of the country which immediately surrounds 
it, and at the same time, also in a very marked degree, peculiar either to this special 
district or to this in common with a few other almost equally isolated, but widely sepa- 
rated districts. 
I cannot devote these prefatory remarks (in which I have the privilege of introducing 
the list and description of my collection, so kindly prepared by the authorities above 
mentioned) to a better purpose than to make as emphatic a statement as I can of the 
isolated character, botanically, of the Roraima district, of the probable botanical relation 
to certain other possibly similar districts, and of the general appearance of the very 
peculiar and distinct vegetation of these districts *. 
The whole area known under the name of Guiana may be likened to a wedge driven 
into the north-eastern shoulder of South America. Geographically, it is thus placed 
between Brazil on the south and Venezuela on the north; for our present purpose it 
will, however, be better to describe its position somewhat differently. The artificially 
formed political divisions of the continent for obvious reasons correspond very closely 
with the tracts naturally differentiated each by its own river-system. As it is along 
the river-systems that the migration of animals and plants chiefly occur, the customary 
and convenient names of these divisions therefore really correspond somewhat closely 
with the natural and important differences in flora and in fauna, which distinguish the 
narrow river-basins. Thus, as Venezuela is essentially the tract drained by the great 
river Orinoco, and as the northern part of Brazil is essentially the tract drained by the 
great river Amazon, and as Guiana, intermediate between these two, consists essentially 
of the parallel tracts drained by comparatively smaller rivers (of which the Essequibo, 
the Demerara, the Berbice, the Corentyn, the Saramacca, and the Maroni may be 
Воррлм Weruam, in 1878. None of these made botanical collections. Dav Вовкк, an English orchid-collector, 
was there in 1881, and brought home interesting living plants, among others, the South-American pitcher-plant 
(Heliamphora nutans), which has, I believe, since been distributed by Messrs. Veitch & Sons. Henry WRHITELY, an 
English collector of bird-skins, was there on several occasions between 1879 and 1884, and is, I believe, again there 
ta the present moment, but he has collected no plants. Өтерет, a German orchid-collector, was there in April 1884, 
and again, with us, in December of the same year. He brought back only living plants, especially the magnificent 
Catileya Lawrenceana, which have since been distributed by Mr. H. Sander. Of these Siedel, the only traveller with 
an eye for plants who has been at Roraima except in the last months of the year, assures me that the abundance of 
flower was much greater there in April than in December. But in the latter month the natives’ Cassava-fields are 
in full bearing, and provision is therefore much more easily attainable. 
* [ use the phrase “ Roraima district ” as including not only the mountain of that name, but the whole of the 
small group of similar sandstone mountains of which Roraima is the best known, and at present the only explored 
member. 
