41 o Journal of Agriculture. [8 July, 1908. 



after the same pattern, exhibit every conceivable combination of parental 

 characters ; they may take after one or other of the parents or they may 

 strike out into new lines. And there is a further important consideration 

 in the fact that, amid the multiplicity of forms, the two original parental 

 types are among them. It is often argued against cross-breeding that it 

 destroys the fixity of the type, that it breaks up the combination of desir- 

 able characters in the original strain at the risk of securing nothing better 

 to take its place. But in the third generation he can now recover the fixity 

 of his original types with all the added vigor resulting from a cross. 



Farrer in speaking of the wheat-plant says — " When two varieties 

 of different types are crossed artificially, although the plants from the 

 seed which are made by crossing may and generally do resemble one another 

 closely, the plants from the seeds they produce usually differ in almost 

 every detail, some most likely, proving to be bald, and others bearded; 

 some quite rust-liable and others rust-resisting; some early and others late; 

 some with stout straw and others with slender; some being tall and others 

 short ; some with long ears and others with short — differ, in fact, in almost 

 every quality." 



The breeder takes advantage of all this variation, selecting such forms 

 as possess the desirable qualities he is striving for and rigidly destroying 

 all those forms that are undesirable. The whole secret of the breeder's 

 art lies in the use he makes of these varying forms, for he knows that 

 by selective breeding, by choosing the natural variations suited to his pur- 

 pose, he can afterwards render them consitant. It is by crossing, selecting 

 and fixing that he attains his ideal and the greatest of these is selecting, 

 for he must first make a judicious selection of the parents to be crossed 

 and afterwards select the best from the products of the cross. 



Mendel's law is applicable to animals as well as plants, but it is not 

 of universal application, and it is rather premature to say that because a 

 certain result happens in the breeding of races of plants, that a similar 

 rtsult will follow in the human race. 



P)REEDING FOR RUST-RESISTANCE. 



But we are more concerned here with the facts which Mendel discovered 

 than the mterpretation he put upon them and a practical illustration may 

 be given. Biften ot the Agricultural Department of Cambridge University 

 has been working upon the improvement of cereals, particularly of wheat, 

 and has been carrying out the principles enunciated by Mendel. He 

 has shown that following the pairs of characters in wheat follow the 

 Mendelian law, the dominant character being placed first in each 

 case — beardless and bearded ears, red and white chaff, presence and 

 absence of hairs on chaff, and red and white colour of grain. He has 

 also applied the principles with success, from a commercial point of view, 

 in two different directions, in the one case to rust-immunity and in the 

 other to " strength " of flour. 



Let us take the rust problem as an example. There are at least thiee 

 different kinds of rust which attack wheat, the Black rust {Pucciuia 

 graminis), the Brown rust {P. triticind) and the Yellow rust {P. glumarum). 

 Only the two former occur in Australia and it is the so-called Black rust 

 which is so injurious in certain seasons, while the Brown rust is compara- 

 tively harmless. It appears that in Britain and America the Yellow rust 

 does considerable damage and it is the one which has just been made the 

 subject of exact experiment by Biffen. He found in his plots a strain of 

 Avheat which was immune to this rust, for although under observation for 



