282' 



PLANT SOCIOLOGY 



high lime content, by the Quercus coccifera association. The latter is 

 able to regenerate repeatedly after fires by sprouting from the 

 roots. 



Perrier de la Bathie (1921) and Humbert (1925) call attention to 

 the tremendous influence of the bush fires in Madagascar. The 

 Madagascar prairie, which today covers four-fifths of the total area 

 of the island and is composed mostly of cosmopolitan tropical grasses, 

 owes its origin exclusively to the periodic bush fires. It lacks almost 

 entirely the old endemic species which do not survive the fire, while 

 the original dry sod, untouched by fire, is composed exclusively of the 

 old Mascarene Tertiary endemics. 



Chevalier (1925, p. 1106) gives some interesting data on the influ- 

 ence of the steppe fires in the Sudan. 



In California, according to Show and Kotok (1924), the hard-leaved 

 chaparral has gained tremendously in extent through fires, while the 

 forest has been reduced. The forest of Douglas fir in the Puget Sound 

 district owes its predominance solely to fires and cannot be regarded as 

 a climax forest. 



Usually fire for the purpose of improving pastures is condemned and 

 probably justly so. In contrast, however, four years' experiments by 

 Hensel (1923) in the North American prairie region show that under 

 certain circumstances fires may increase production. Hensel subjected 

 quadrats to an annual shearing; pasturing was prevented. After 

 four years, with regular burning down each spring, instead of the poor 

 Andropogon furcatus, the better A. scoparius showed an increase of 

 48 per cent; upon the unburned square, however, it had decreased by 

 61 per cent. The number of shoots and dry weights of Gramineae 

 and Cyperaceae showed the following changes in the course of the 

 investigations : 



Table 32. — Influence of Prairie Fires upon Growth of Grasses 



