REVIEWS 789 



tain. These problems are of much economic importance in Indian 

 forestry. 



This study has been one of economic ecology and the results so far 

 attained are published in the article under review. The paper covers 

 such a wide field and is so complete with statistical information, it 

 scarcely permits of adequate review in the space available in the Jour- 

 nal. The reviewer has seen no recent treatment of research on re- 

 generation so complete and suggestive as this report by Mr. Hole and 

 it should be read by all American foresters engaged in research on this 

 subject. 



The plan under which the investigation has been carried out during 

 the past twelve years was well considered and the following definite 

 lines of research undertaken : 



1. Experiments to test the effect of soil composition, soil moisture, 

 soil aeration and light intensity on the development of Sal seedlings. 



2. Experiments in growing seedlings under field conditions in Sal 

 forests both in deep shade and in the open, the experiments being re- 

 peated for several years in order to obtain average results. 



3. Experiments to determine the effects of dominant or limiting 

 factors on seedlings grown in water cultures and pot cultures under 

 control. 



4. Experiments in the field to determine how far the limiting fac- 

 tors can be controlled by methods suitable for incorporating in a prac- 

 tical system of silvicultural management. 



Field experiments conducted during the years 1909 to 1915 indicated 

 that a layer of dead leaves on the soil surface is very injurious to the 

 successful germination of Sal and to its early development; that 

 drought is responsible for the widespread death and dying back of 

 seedlings during seasons of scanty precipitation and that bad soil aera- 

 tion causes large numbers of seedlings to die under shade during rainy 

 ' seasons and many of the survivals to die during the dry season, due to 

 their defective root development. 



Based upon these results, the inference was drawn that the best 

 method for regenerating Sal forests would probably consist in 

 (a) clearing the surface soil of dead leaves and humus, (b) clear 

 felling in strips and small patches, (c) artificial sowing in the cleared 

 areas combined with weeding in the first year. In regions where the 

 above were impracticable due to cost, it was pointed out that the num- 

 ber of Sal seedlings could be rapidly increased merely by the continued 

 removal of the dead leaves by light leaf fires. 



