72 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



the work of the Section. Crop parasites were collected and 

 identified and advice given to the officers of the Department 

 and the general public as occasion required. 



(1) Ufra of rice. Evidence was obtained both in pot 

 cultures at Pusa and in a field experiment carried out in 

 collaboration with the Bengal Department on Dacca farm 

 that this disease can be sometimes conveyed by seed from an 

 infected crop. 



The laboratory work at Pusa during the past season was 

 directed chiefly to a study of the conditions which enable 

 or induce the parasitic eelworm (Tylenchus angustus Butl.) 

 to leave the water of the paddy fields and ascend the plant 

 to reach its susceptible portion near the apex of the shoot. 

 In last year's report it was explained that atmospheric 

 humidity immediately aroufld the plant was the determin- 

 ing factor, the worm being unable to move out of water 

 except at high humidities.. 



The exact measure of the humidity of the air on the sur- 

 face of a plant is exceedingly difficult. It is, however, pos- 

 sible to grow paddy in enclosed chambers and measure the 

 relative humidity of the air within the chamber. It is also 

 possible to watch the movements of worms on glass slides 

 kept in similar chambers. By these methods, using a Poly- 

 meter, it was found that the worms can move freely when 

 kept on glass slides at a relative humidity of 95 (tempera- 

 ture 87° to 90° F.), but not at all at 90, the exact point 

 being apparently near 93. On the living plant they can 

 move at lower air humidities, certainly below 90 but not at 

 75, at the same temperature. If they can soon reach the 

 inner folds of the shoot (which is only possible in young 

 seedlings), they become less dependent on high air humidity 

 than when they remain on the exposed surface, no doubt 

 because the vapour of transpiration causes the confined air 

 within the folds to reach a higher degree of saturation than 

 that of the surface. 



Temperature also influences movement but less regu- 

 larly. For instance, worms when free in water are much 



