484 PHYTOGEOGRAPHICAL REMARKS. 



are found in large numbers and occasionally Conobea aquatica and Bacopa 



aquatica. 



In those places where the banks are very low and consequently the 

 wood is under water for a great part of the year, the trees are much 

 smaller. Such plains grown with low trees and shrubs can extend to large 

 distances from the river. 



The border of wood along the river is generally very broad, but its 

 breadth has been accurately determined in a few places only by cutting 

 roads from one river to another. In the southern part of the alluvial strip 

 the older stone formations reach the surface in some places. The stone has 

 undergone at its surface a peculiar process of decay by which the soil has 

 become unfit for the germination of the seeds of large trees. Besides the 

 porosity of this soil which causes a relative drought in some periods of the 

 year, the abundant rainfall has dissolved and removed a great part of the 

 salts wanted by plants, so that great sterility is another cause by which 

 the growth of trees is prevented. These plains which as a rule are situated 

 somewhat higher than the surrounding alluvium, so that in the wet season 

 they are not flooded and consequently the river does not deposit mud on 

 them, are generally called „savannahs" in the colony, although the climate 

 makes it evident that from the point of view of plant geography they differ 

 very much from the true savannahs in the south of British Guyana and from 

 the Campos of Brazil. That here only the above mentioned influence of the 

 soil can be the agent is sufficiently proved by their small extent and by 

 the fact, that they are entirely enclosed by wood. 



The best known of these savannahs are of course those that are situa- 

 ted on a riven as the Joden-savannah and the savannah of the Upper Para 

 river. But also in various expeditions through the country such treeless 

 plains have been repeatedly met with, so that at the present moment it is 

 very difficult to tell what part of the colony is occupied by the savannahs ; 

 opinions on this point differ widely. In the east of the colony this region 

 is situated nearer the shore than in the west and one of the savannahs of 

 the Upper Commewine seems even to extend as far as the mouth of the 

 Marowine and there to form the above mentioned sandy beach of Galibi. 



Without vegetation these savannahs are only in a few places, according 

 to Kappler. As a rule Gramina and Cyperaceae are strongly developed and 

 form a dense cover between which numerous herbs and low shrubs are 

 found. Among the ferns on them a number of species of Schizaea must be 

 mentioned, further species of Xyris, Eriocaulaceae as Paepalanthus and 

 Syngonanthus, Commelina, Trema micrantha, different Amarantaceae ; among 

 the Caryophyllaceae Drymaria and Polycarpaea, Anonaceae, among which 

 especially Xylopia, Mimosa in different species. Of the genus Cassia espe- 

 cially Cassia cultrifolia, C. uniflora, C. flexuosa, C. glandulosa nnd C. patel- 

 laria are represented, among the Papilionatae Stylosanthes, Zornia, Desmodium, 

 Clitoria, Centrosema, Calopogonium, Dipclea and Eriosema. The Rutacea 



