INSTITUTE, PUSA, FOR 1916-17 57 



When the rice worm was first described (Pusa Bulletin 

 No. 34, 1913) no other instance was known of injury to 

 cultivated plants caused by an eel worm with the peculiar 

 surface- feeding habits of Tylenchus angustus. Quite 

 recently, however, a second case has been recorded, on cur- 

 rants, near Cambridge (England). It seems probable that 

 others will be discovered, now that attention has been 

 directed to the economic importance of this type of nema- 

 todes. An account of the present stage of the investigation 

 is in preparation for publication. 



(2) " Tokra " of tobacco and mustard. Further 

 experiments were carried out by Dr. Shaw with the object 

 of testing the claim that sodium nitrate was a specific 

 against this pest. The results of the previous season's 

 work had been partly obscured by the fact that the amount 

 of " tokra " appearing in a plot seemed to depend as much 

 upon the degree of infection in the soil as upon the influence 

 of any application of sodium nitrate. During the season 

 1916-17, the experimental plots were so arranged, in the 

 light of the information gained during the previous season, 

 that this factor was eliminated. It was then found that 

 the amount of "tokra"' which came up in any particular plot 

 depended largely upon the degree of infection in the soil 

 and was practically uninfluenced by any application of 

 sodium nitrate upon an agricultural scale. 



The species of Orobanche examined were 0. cernua 

 Loeffl. and 0. indica Ham. and, as in the previous season, 

 the former proved to be restricted to Solanacece while the 

 latter occurred principally upon Cruciferce and only to a 

 modified extent upon Solanacece. With a view to testing 

 the parasitism of these species in greater detail than was 

 possible within the limits of a field experiment, a series of 

 pot cultures was carried out. Four host plants were used, 

 namely tobacco, cabbage, mustard and turnip, and these 

 host plants were infected with seed of 0. cernua acd 

 0. indica which had been collected from " tokras " parasitic 

 both upon the species of host plant infected and upon the 

 other three host plants. Thus pots containing tobacco 



