43 



Howard and Howard 1 have attributed to aeration difficulties 

 the "wilt disease" of Java indigo and certain other 

 agricultural difficulties encountered on the heavier 

 and better-watered soils of India. These authors also 



refer to disturbances of aeration the toxic effect of 



2 3 



grasses on trees under which they grow. MacDougal 



suggests that poor aeration due to puddling of the 

 soil while under water may explain the slowness with 

 which plants are establishing themselves on the beaches 

 now emerging from ten years submergence by the Salton 

 Sea. On the other hand, the benefits of good drainage, 

 looser texture and the like are frequently ascribed to 

 improved aeration^. Soil improvement by earthwurms has 

 been referred to the effect of their burrows in increas- 

 ing aeration. 5 



~" T~. Agr. Res. Inst. Pusa (India), Bull. 52_: 

 35 pp. 1915. 



2. On this toxic effect see Pickering and the 

 Duke of Bedford,- Jour. Agr. Sci. 6: 157 (1914), and Rus- 

 sell,- Soil Conditions and Plant Growth, 2nd ed., pp. 113- 

 116 (1915). 



3. Geog. Review 2: (1917). 



4. See authors cited on page • , note , 

 especially the articles of Wollny. 



5. Wollny, Porsch. Geb. Agr. Phys. : 382 



(1890); Djemil,- Ber. Physiol. Lab., Vers. Sta. Halle 



(1898); Priend,- Sci. Prog. 6_: 3y3-401 (1912). 



