Albert Howard 383 



the individuals grown in flower-pots showed much less rust than the same 

 unit species grown in the field and the difference was most marked. In 

 flower-pots the roots of the wheat plants obtain a copious supply of air. 

 This apparently increases the resistance of the plant, the rust colonies 

 remain small and few in number and ripening of the grain takes place 

 normally. When grown in the field, the aeration of the roots is reduced, 

 the rust runs much more rapidly and the grain is often shrivelled. 

 Similar differences in rust resistance are observed between plots of the 

 same unit species when grown on heavy land with or without deep 

 cultivation after the rains before sowing. The better the physical con- 

 dition of the subsoil, the greater the rust resistance. This matter is being- 

 followed up further and the connection between rust attacks and the 

 distribution and character of the root-system is being investigated at 

 Pusa. Some interesting facts have already emerged. Several of the most 

 rust-resistant wheats at Pusa are very shallow-rooted, some of the most 

 rust-liable types from the black soils are exceedingly deep-rooted. Soil- 

 aeration appears therefore to play an important part in the relations 

 between the host and the parasite in rust attacks. 



In the case of the linseed crop, the matter is being carried further. 

 A large collection of the linseeds of India has been made at Pusa and 

 the various unit species have been isolated and classified. The unit 

 species fall into three groups according to the size of the seed and the 

 character of the root-system. The linseeds of the black soils of Central 

 India possess large seeds and a deep root-system which enables the crop 

 to withstand the cracking of these soils. The types found in the plains 

 have small seeds and a shallow root-system (Fig. 5). The third group is 

 intermediate in all respects. When grown at Pusa in alluvial soil there 

 is a great difference in the appearance of these groups of linseed. The 

 small-seeded class is very luxuriant and does not suffer from rust and 

 other diseases. The large-seeded deep-rooted class grows and sets seeds 

 with difficulty. The plants appear starved and are often attacked by 

 rust (Melampsora Lini Desm.). There is a very great difference in the 

 appearance of the active roots of the deep-rooted types of linseed 

 attacked by rust and the shallow-rooted types which escape this disease. 

 The former appear starved and there is extensive discolouration. The 

 latter are turgid, white and exceedingly vigorous. 



Red rot of sugar-cane. One of the difficulties in sugar-cane cultivation 



on the black soil areas of the eastern tracts of the Central Provinces is 



the prevalence of red rot (Colletotrichum falcatum Went.), which, as is 



► well-known, attacks the cane during the ripening period and leads to 



