THE METHOD OF CLEARINGS. 373 



seeds ripen, and on the transportability, i. e. weight and shape, of 

 the seeds. Seeds will of course be carrried furthest when the 

 wind blows down a slope. 



(ii) Gravitation. For this cause to be effective the coupe 

 should be situated at the foot of, or on, a slope, with fertile trees 

 standing above. If it is on a slope, the seeds should be caught in 

 the ground and not go on rolUng or slipping down to the bottom ; 

 so that the steeper the gradients are, the rougher must be the 

 hillside, or the smaller, hghter, flatter or otherwise clinging the 

 seeds. 



(iii) Surface drainage. Heavy rain falling on saturated soil 

 will always tend to wash down seeds to lower levels and the quan- 

 tity arrested in any place will depend on the obstacles presented 

 by the roughness of the ground or an abundant covering of herbs 

 and shrubs, on the size, weight, shape and nature of the seeds, 

 and on the amount of overflow. If the soil has been hardened 

 and cleared of all low vegetation by heavy grazing or fire, the 

 seeds will mostly be washed away into the streams and hollows, 

 especially if, like teak, they cannot anchor themselves quickly by 

 early germination. Those seeds which are carried into streams 

 that spread out over wide areas, will be deposited in slack water 

 and left high and dry when the flood waters subside into the 

 regular channels, as happens on a large scale in respect of sissu 

 and Acacia Catechu where Himalayan streams debouch into the 

 plains, and of tamarisk and Acacia arabica in the Indus valley. 



(iv) The alternate ebb and flow of the tides. This cause is 

 effective on low coasts and in estuaries and deltas of rivers. 



In addition to the effectiveaess and certainty of action of the 

 causes just considered, successful regeneration presupposes a suit- 

 able soil and favourable climatic conditions. 



Value and employment of the method. From the foregoing it 

 is evident that this method cf regeneration can be resorted to only 

 in those very rare instances, in which all the prevailing conditions 

 are exceptionally favourable. As it is impossible, or next to im- 

 possible, to say for certain whether they are so, the risk run in its 

 employment is so great that a slight error of judgment may result 

 in the utter ruin of the coupe, and even if the best happened, it might 

 be more than a quarter of a century before the ground got covered 

 again. Subsequent resort to artificial regeneration would, owino 

 to the deterioration of the soil and the presence of weeds, be ex- 

 ti'emely difficult and costly. The frequently fiooded islands and low 

 ground in the deltas of our great rivers, the chaors and kachas of 



