474 



Cross-fertilisation of Wheat. [nov., 



fifty which are mixed dominants and recessives and will not 

 breed true, so far as we can see, at any time of their subsequent 

 history. For practical purposes these can be discarded, and our 

 whole attention can be fixed on the " recessive " form, if that 

 be what we want, which we can obtain fixed in the second 

 year, or on the " dominant," if that be the form we want, which 

 can be obtained definitely fixed in the third year. Anyone 

 with a mathematical turn of mind can see what complications 

 are introduced if two parents possessing, say, six or even twelve 

 Mendelian "dualities" are crossed, each of the six or twelve 

 dualities giving in the third generation its 25 per cent, fixed 

 dominants, 25 per cent, fixed recessives, and 50 per cent, un- 

 fixed forms. The calculation can be made, and the botanist 

 making the cross can know beforehand what he will obtain,, 

 and calculate with reasonable precision, making allowance for 

 losses by birds, killing of plants, and similar mishaps, the number 

 of varieties he will get. One most important point is to ascer- 

 tain which of the many differing characteristics of wheat are 

 true " Mendelian " ones, and having regard to the fact that this 

 way of regarding the cross-breeding of wheat has been con- 

 sidered for four or five years only, it is not at present certain 

 whether the list is complete or definitely accurate, but a great 

 mass of material is available, and it is believed that wheats can 

 be bred to order. 



It makes no difference to millers whether the wheat is bearded 

 or beardless, has red chaff or white, lax ears or dense, a rough 

 leaf surface or a smooth one, a thick hollow stem or 3 thin and 

 solid one, nor, having regard to the fact that some English 

 white wheats are quite as strong or stronger than many or any 

 red ones, whether the colour of the bran be red or white ; but all 

 these points and many more, including immunity and suscep- 

 tibility to attacks of yellow rust, are being duly considered, with 

 the object of producing a wheat acceptable to the farmer as 

 well as to the miller. 



The all-important point is whether " strength " and its oppo- 

 site, weakness, is a " Mendelian duality." As yet, sufficient 

 material is not available to enable the point to be settled 

 definitely as a result of milling and baking trials, but the 

 evidence based on appearance and chemical analysis is dis- 



