148 THE RURAL PROBLEM 



spicuous by an abundant outbreak of reddish-yellow pustules all 

 over the foliage. In certain seasons and with certain varieties 

 the outbreak may be so severe as to very greatly diminish the 

 yield of grain. In the bad rust year of 1891 the loss due to this 

 cause in Prussia alone was calculated at over £20,000.000, while a 

 well-known authority estimates that the average loss from rust 

 to the wheat crops of the world would not be covered by 

 £100,000,000. No prophylactic against the disease has been 

 discovered, and it is recognised that the only way to avoid it is 

 to make use of varieties which are naturally immune. Unfor- 

 tunately the few such varieties that exist are in other respects 

 poor and unprofitable to grow. 



Professor Biffen began his experiments by crossing a variety 

 peculiarly subject to the attacks of yellow rust with an immune 

 variety. The hybrids produced were all severely attacked by 

 rust. In the following year such seed as could be collected from 

 these plants was sown. The greater number of the resulting 

 plants were much rusted, but some were entirely free from the 

 disease, though growing up in the closest contact with their 

 rusty brethren. It was found on counting that the immune 

 plants formed almost exactly a quarter of the total number. 

 In other words, the experiment proved susceptibility and immu- 

 nity to be a pair of Mendelian characters, and consequently within 

 the control of the breeder to combine with other characters 

 according as he pleased. The fact that resistance to yellow rust 

 is a unit character exhibiting Mendelian inheritance makes it a 

 simple matter to transfer it to wheats which are in every way 

 desirable except for their susceptibility to rust. From the 

 knowledge gained through his experiments Professor Biffen 

 has been able to build up wheats combining the large yield and 

 excellent straw of the best English varieties with the strength of 

 the foreign grain, and at the same time quite immune to yellow 

 rust. During the present year several acres of such wheat coming 

 true to type were grown on the Cambridge University Experi- 

 mental Farm, and when the quantity is sufficient to be put upon 

 the market, there is no reason to doubt its exerting a considerable 

 influence on the agricultural outlook. 



Besides the work on wheat, experiments have been undertaken 

 with barley. As with the wheats, there are varieties of barleys 

 with glutenous and others with highly starchy grains. The more 

 starch a barley contains, the more valuable it is for mailing 

 purposes. Since Professor Biffen has been able to demonstrate 

 that with barley, as with wheat, starchiness is recessive to 

 glutenous quality, it should be an easy matter in the future to 

 associate tlie starchy character with other valuable properties in 

 barleys. 



Nor is the work at Cambridge confined to plants. A start has 

 been made with the object of investigating the inheritance of 

 horns and of face colour in sheep, and Professor Wood has been 



