THE ECOLOGY OF THE UPPER GANGETIC PLAIN. 319 



could develop naturally. Such a flora now represents the climatic 

 climax as degraded and modified by man. It is the resultant of the 

 struggle between the vegetation on the one hand developing toward 

 some type of climatic climax forest, and the retrogressive influence of 

 the intense human factors on the other hand, continually interfering 

 with and destroying it. This balance between man and the natural 

 vegetation is very delicate, and may perhaps help to explain many 

 of the very serious human problems of the area. After a series of 

 favourable years, the slightly increased vegetation allows a corres- 

 ponding increase in the human and animal population, and results 

 in increased demands on the plant resources. Then subsequent bad 

 years leave the men and animals with insufficient food, and if many 

 do not die as the direct result of famine, they are left so weakened 

 as to become easy prey to- pestilence, and are again reduced in 

 numbers. In other words, under present conditions, the human and 

 animal population is about as large as the area can support. Improved 

 methods of agriculture, and intelligent protection and conservation 

 of the plant resources appear to the only solution of the problem. 



Pioneer monsoon deciduous forest stage. If left to itself, it 

 is very probable that the thorn scrub would in turn be replaced 

 by some form of higher and more mesophytic forest. Schimper 

 concludes (10) that if the annual rainfall is below 90 cm., " xerophi- 

 lous scrub", especially " thorn forest" and "thorn bush," prevails ; 

 with 90 — 150 cm. there is a struggle between "xerophilous woodland" 

 and grassland, with the former prevailing when there are greater 

 heat and longer rainless periods during the vegetative season. With 

 180 cm. or more rainfall, a high forest is produced. Brandis (1) 

 says that " really thriving forests are only found where the fall 

 exceeds 40 inches, and a rich luxurient vegetation is limited to those 

 belts which have a much higher rainfall. " 



The highest type of vegetation about Allahabad, the scrubby 

 xerophytic shrubs and trees, would, I think, correspond roughly to 

 Schimper's " thorn scrub. " Doubtless in most regions treated by 

 Schimper, the vegetation described as climax actually is climatic 

 climax. He was recording situations as they actually are ; some of 

 them at least are not necessarily climatic climaxes but modi- 

 fied claimaxes due to retrogressive influences. To class the 

 thorn scrub of the Upper Gangetic Plain as the true climatic cli- 

 max is a mistake. On Schimper's classification, the rainfall in 

 the area about Allahabad should produce a forest somewhere 

 between ' xerophilous scrub" and "xerophilous woodland ". It is 

 difficult to determine exactly what these terms mean. Probably 

 each writer must provisionally fix his own limits to them. Certainly 



