OBSERVED DURING THE RORAIMA EXPEDITION. 255 



entirely covered by a gravelly layer of shattered conglomerate, a very beautiful herb, 

 with dowers of an intense violet-blue — a very rare colour in Guiana — was common, and 

 pleasantly reminded me of an English " viper's bugloss." It was Slachylarpheta mutabilis, 

 Vahl [No. 1], which seems to me to correspond to my description of a localized species. 



Again, between the Ireng and the Cotinga rivers, there grew in abundance, and 

 evidently as a native, a plant [Farcrcea gigantea] which, common enough near the coast 

 of Guiana in cultivation, and even as an evident escape from cultivation, is nowhere else, 

 as far as I have seen in many wanderings, wild in that colony. 



Lastly, as regards localized species, I would mention several dwarf bamboos, none of 

 which, unfortunately, did I succeed in finding in flower. One of these, a wonderfully 

 graceful species, appears to me peculiar, in that it grows in dense thickets on the open 

 savannah. This was on the Ireng river, and more sparingly onward from there toward 

 the Cotinga. Another of these bamboos (Chusquea [sp. ?], No. 18), I think the most 

 graceful plant I ever saw, occurred sparingly, and only in one spot, on the Arapoo river 

 close to the village of Tooroiking. A third bamboo, a climbing form ( Guadua) [No. 359], 

 occurred to me first on the same river, but is much more common on lloraima itself, and 

 should perhaps be spoken of in connection with the vegetation of that mountain. 



Turning next to the areas of distinct vegetation, the first to be mentioned is that of 



the Kaieteur savannah *. This is certainly a very remarkable place, with an equally 



remarkable vegetation. It is an open space, some two miles long by one across, in the 



heart of the ordinary dense forest, and some four days' journey on foot from the nearest 



open country. It has been said that the descent from the tableland of the interior 



toward the sea is not a gradual slope, but occurs chiefly in a series of step-like 



descents. These descents are generally of no great individual height ; but that 



of the Kaieteur takes the form of an almost abrupt cliff — at the Kaieteur fall itself it 



is an actual cliff — of between seven and eight hundred feet in height. The Potaro river, 



rising apparently from the neighbourhood of, but not actually on, Koraima, after an 



unknown upper course of considerable length, runs along one side of the almost 



perfectly level Kaieteur savannah, and precipitates itself, at the east end of that savannah, 



down the sheer descent of 800 feet. The savannah itself is virtually a flat exposed rock, 



many parts of which are as absolutely bare as a London pavement. This rock is 



sandstone, which, as in the eppellings (indeed it probably is one, but of unusually 



unbroken surface) is capped by a harder material, a layer of conglomerate. Just as 



the bard surface of the eppellings cracks, and eventually affords roothold in the fissures 



thus made for plants, so the hard conglomerate covering of the Kaieteur savannah has 



cracked, and in many of the fissures thus produced has given harbourage for plants. Some 



of these latter fissures have gradually been tilled up by the accumulation of vegetable 



matter ; others remain still open. On this savannah, however, the fissures are larger 



than is commonly the case in the eppellings — are, in fact, often very long but generally 



narrow fissures. Many of these are now entirely occupied by shrubs and dwarf trees. 



The lines of these masses of vegetation, necessarily following the direction of the fissures, 



* Some excellent " Remarks on the aspect and flora of the Kaieteur Savannah " were published by my friend 

 Mr. G. S. Jenman in 'Timeum' vol. i. (1882) p. 229. 



