112 OROBANCHE AS A PARASITE IN BIHAR 



remaining plots being used for mustard and cabbage. This increase consisting 

 as it does principally of 0. cernua is to be attributed to the seeds from last 

 year's "tokras," which fell into the soil as the fruits ripened and germinated 

 next season with the second crop. 



Although it was evident, from an inspection of the numbers of "tokras" 

 in the neighbouring plots of mustard and cabbage, that large quantities of the 

 seed of 0. indica were in the soil yet in proportion very few plants of 0. indica 

 occurred in the tobacco. This bears out the conclusion of the previous season 

 that this species is not normally a heavy parasite of tobacco. Yet a field of 

 tobacco was found near Pusa in which the crop had been very severely damaged 

 by 0. indica — there being hardly any 0. cernua present. These facts must be 

 considered later when describing the results of the pot cultures. 



The fact that the bulk of the 0. cernua was in one corner of the unmanured 

 plot, and the bulk of the 0. indica was scattered over the manured plot, cannot 

 but suggest that the degree of local infection in a particular field is a very 

 potent factor in the number and distribution of the " lokras " which appea-r 

 and that the differences between the two plots in this experiment might be due 

 to some factor other than the application of nitrate. 



(6) Mustard {Brassica campestris var. glauca). Of the two plots under 

 mustard that on the east (Plot D), received 10 lb. of sodium nitrate scattered 

 on the surface and mixed with the soil immediately before sowing. The 

 germination was good and the crop came into flower on, 24th November, 

 the first "tokra" showing above the surface about the same time in both 

 the manured and the unmanured plot. From the end of November onwards 

 there was a steady appearance of "tokra," all of which was 0. indica. On 

 February I'ith the mustard was cut and the number of mustard plants aiul 

 "tokras" in each plot was counted, the results were as follows : — 



Number of mustard plants Number of 0. indica 



Manured (D) .. 1,949 2,012 



Unmanured (C) . . 1,634 3,070 



The weight of the mustard cut from each plot amounted to about 8i 

 maunds. From the above figures it cannot be contended that the sodium 

 nitrate had any very marked effect on the appearance of the "tokras," while 

 the number of "tokras" which came up showed that their non-appearance 

 in the previous season, when the plots were under tobacco, was not due 

 to lack of infection in the soil but rather to lack of a suitable host. 



(c) Cabbage {Brassica oleracea). Cabbage seedlings were planted out 

 in two of the plots toM^ards the end of November. There were 200 seedUngs 



