Chap. Ill] TROPICAL WOODLAND AND GRASSLAND 273 



forest that replaces it on moister soil, extends over the interior of the 

 provinces of Parana and Santa Catarina (Araucaria-savannah) to Rio 

 Grande do Sul, where, owing to the cessation of tree-growth, it passes 

 over into a purely grass steppe, the pampas. 



To the north-west, on the other hand, in the Sertao district, which 

 occupies the interior of Brazil between Minas Geraes and the basin of 

 the Amazon, the savannah gradually gives way more and more to thorn- 

 forest and thorn-scrub. Whence arises this difference between the 

 vegetation of the southern and northern provinces in the interior? why 

 in the southern provinces does grassland predominate — although in the 

 form of savannah it is not quite destitute of trees and is interspersed 

 with savannah-forest — whilst in the northern provinces woodland pre- 

 dominates ? The climatic differences afford a decided answer. 



The campo-district has a climate admirably suited to grassland, in 

 particular, frequent precipitations and moderate heat during the vegetative 

 season ; on the other hand, the climate includes a factor unfavourable for 

 woodland, in the dry cold winter 1 . 



Tropical Grassland Climate. 



BRAZILIAN CAMPOS (SAO PAULO). 



2 3° 36' S., 46 25' W., 745 meters above sea-level. 



(From Meteorol. Zeitschr., 1891, p. 146.) 



Evaporation : 1887, 545-2 mm. ; 1888, 454-0111111. 



According to the five years' observations of Joyner (Meteorol. Zeitschr., 1886, p. 312) 

 the mean lowest temperatures are — May, 2-7 ; June, 1-7 ; July, 2-1 ; August, 0-7. 



1 See p. 174. 



