Grass 
rushes near sheets of fresh water, and other grasses 
also occur in wet places. Then, on the other hand, 
the bent-grass, Psamma, grows in very dry ground, and 
a sand-dune overgrown with it is not unlike a steppe. 
All these are natural grass-lands. 
But in the United States the prairie, which is a 
typical grass-land, is bounded on the east or Atlantic 
side by a country which is or used to be a thick and 
well-grown forest. On the Rocky Mountains or western 
side, the prairie becomes gradually more and more 
steppe-like and arid until real desert begins. It is 
just the same with the pampas of the Argentine. In 
the west at least it shades off into a desert, whilst on 
the east there are or used to be the forests and woods 
of the Rio de la Plata. 
It seems very probable that a considerable proportion 
of the eastern prairie, and very likely of the Argentine 
pampas as well, was once woodland or forest; at any 
rate many American botanists seem to think so. The 
Indians used to set fire to the woods in order to 
obtain land for cultivation. Prairie fires, happening in 
a late and dry summer when everything is scorched 
and inflammable, would inevitably prevent the growth 
of woodlands. If this is so, it is only a natural grass- 
land in the sense that xatural man, not the intelligent 
and civilised variety, has produced it. 
The author has himself seen the effect of grass fires 
upon the African plateaux in Uganda, It is not a 
very alarming or dangerous spectacle, for it is just an 
insignificant line of blazing grass which may be some- 
times checked by a hard-trodden native path, and which 
one can step over without any danger. 
In that district, each river is bordered by a fringe of 
woodland ; the fire does not usually destroy the foliage 
but only singes the outlying branches of the outside 
267 
