i88 MENDELISM chap. 



will naturally influence his procedure. Or, again, 

 his experiments may show him that one of the 

 characters he wants, like the blue of the Andalusian 

 fowl, is dependent upon the heterozygous nature of 

 the individual which exhibits it, and if such is the 

 case he will be wise to refrain from any futile 

 attempt at fixing it. If it is essential, it must be 

 built up again in each generation, and he will 

 recognise that the most economical way of doing 

 this is to cross the two pure strains so that all the 

 offspring may possess the desired character. The 

 labour of analysis is often an intricate and tedious 

 business. But once done it is done once for all. 

 As soon as the various factors are determined upon 

 which the various characters of the individual 

 depend, as soon as the material to be made use 

 of has been properly analysed, the production and 

 fixation of the required combinations becomes a 

 matter of simple detail. 



An excellent example of the practical application 

 of Mendelian principles is afforded by the experi- 

 ments which Professor Biffen has recently carried 

 out in Cambridge. Taken as a whole English 

 wheats compare favourably with foreign ones in 

 respect of their cropping power. On the other 

 hand, they have two serious defects. They are liable 

 to suffer from the attacks of the fungus which causes 

 rust, and they do not bake into a good loaf. 

 This last property depends upon the amount of 

 gluten present, and it is the greater proportion of 

 this which gives to the " hard " foreign wheat its 

 quality of causing the loaf to rise well when baked. 

 For some time it was held that " hard " wheat with 



