4 



Introduction. 



Still more important for the future wheat supply of the world 

 are the questions whether it is possible to breed early ripening 

 varieties and varieties resistant to rust — a pest which at present 

 often seriously reduces the crop and is particularly troublesome 

 in South Africa and India. If the process of maturation can be 

 hastened only a few days, it becomes possible to extend the 

 wheat belt further northwards and to escape the harvest frosts 

 which sometimes cause so much trouble in Canada. Drought- 

 resisting* wheats are also wanted — varieties with narrow leaves 

 and therefore less likely to lose water by transpiration. 



The improvement of wheat by selection, in other words the 

 search for new mutation forms, is going on in all parts of the 

 world, but was necessarily uncertain so long as progress depended 

 on accident. The re-publication of Mendel's work, however, has 

 given an impetus to the study of cross-breeding and it is now 

 possible to predict the way in which certain characters of the 

 parents will appear in the offspring. It is not too much to say 

 that when the virgin regions of the world are all inhabited the 

 total production of wheat will be limited only by the limit set 

 to the plant-breeder's work. 



Speculation as to the future world-supplies of wheat are always 

 interesting, but are particularly liable to be falsified. The factors 

 are incompletely known. We are only now beginning to make 

 soil surveys. Yet without some sort of a world survey it is 

 impossible to say what area is suitable for wheat culture. It is 

 not known how far improvement of the cropping power of the 

 plant is possible, and whether we can ever hope to exceed the 

 present run of yields under our present conditions of soil and 

 climate. Nor is it known whether varieties can be found or made 

 to grow in regions at present unsuitable, as, for instance, in 

 northern latitudes where the summers are short though the days 

 are long, or in the vast areas of the world where the rainfall is 

 too small. It is especially difficult to attempt forecasts at the 

 present time, when the dominating factor in the world's supply 

 is the essentially transient supply sent in by pioneer workers in 

 new countries. However, all countries are alive to the importance 

 of the problem, and work on the subject is beginning in most of 

 them. 



