48 REPORT OF THE AGRICULTURAL RESEARCH INSTITUTE 



raking it into heaps and burning it. It can perhaps be 

 equally effectively carried out by early ploughing so as to 

 bury the debris of the previous crop. Both these methods, 

 however, are likely to interfere, if carried out on a large 

 scale, with the local fodder supply and it seems necessary 

 to ascertain whether diseased straw can safely be fed to 

 cattle. There will be no need to defer active operations 

 while such relatively minor points are being investigated, 

 and it is horded that the destruction of the stubble will be 

 attempted on a large scale in the near future. 



(2) " Tokra " of tobacco and mustard. The work of 

 past two seasons has established that the parasitic species 

 of Orobanche in Bihar are 0. indica Ham. and 0. cernua 

 Loeffl. The species 0. cernua is the common parasite of 

 solanaceous crops in Bihar but does not appear to attack 

 Cruciferoe save in very exceptional circumstances. In a 

 crop of mustard, grown in a field known to be badly infected 

 with both species of Orobanche, only four cases of 0. cernua 

 were found among many thousands of 0. indica. The 

 parasitism of 0. cernua therefore is more restricted than 

 is that of 0. indica which, while being a serious parasite of 

 Cruciferce, does occur to a not inconsiderable extent on 

 SclanacecB. The life histories of the two species seem to 

 be identical, the " tokras " appearing a few weeks after 

 the host crop is well established and rising to flower and 

 fruit along with it. Both species rely on the production 

 of countless millions of minute seeds for their dissemina- 

 tion and perennation. These seeds are present all over the 

 cultivated lands of Bihar, their number and minute size 

 being- extremely favourable to their dispersal in the strong- 

 winds of February and March when the fruits of 

 Orobanche are ripe. 



Experiments were carried out during the year with a 

 view to discovering whether the addition of quantities of 

 sodium nitrate to crops of mustard and tobacco had any 

 influence on the number of " tokras " which occurred in the 

 crops. Plots of equal size were selected in land which was 

 known to be infected with both species of Orobanche and 



