HOWARD, HOWARD AND ABDUR RAHMAN. 320 



been due to the fact that it was not understood that the cotton crop 

 in Egypt is a mass of hybrids some of which are exceedingly un- 

 desirable. Two difficulties therefore face the introducer of an 

 exotic in which natural crossing occurs. The introduced crop is 

 almost certain to contain splitting forms, some probably 

 undesirable. Further the exotic will probably cross with the local 

 crops. 



The effects of natural crossing in the introduction of exotics 

 are often erroneously attributed to the influence of acclimatisa- 

 tion. It is obvious that the effects of acclimatisation can only be 

 studied in a crop in which natural crossing is altogether prevented. 



3. The testing of varieties. 



Varieties can only be safely collected and tested side by side 

 at an Experiment Station if cross-feiiiilization either does not occur 

 at all or to so small an extent that an occasional rogueing of the 

 plots is sufficient to keep them pure or if, as in tobacco, it can be 

 prevented altogether by artificial means. Variety trials of crops like 

 maize and castor oil are difficult on account of the ceii;ainty of 

 contamination by vicinism. Much useless work is continually 

 being done in the trial of varieties which cross among themselves* 

 The constitution of the crop and therefore the yields change from 

 year to year and the results are erroneously attributed to the vary- 

 ing influence of the season. 



4. The Distribution of Seed. 



The final outcome of the improvement of any crop in India 

 is naturally the growth for distribution to the culti\ators of im- 

 proved and tested seed. The investigator, not unnaturally, is 

 anxious to begin this work at the earliest possible moment as it 

 is regarded as a proof of the successful consummation of his efforts. 

 In crops like wheat and tobacco there are no particular difficulties 

 in the seed supply except in distributing wheat in the Canal Colonies 

 01 the Punjab where natural crossing is comparatively common. A 

 large supply of self-fertilized tobacco seed is easily produced, and 

 the scattered nature of the cultivation and the few plants kept for 



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