HIS THEORY OF HEREDITY 117 



wheat in this country will be increased by several 

 shillings to the acre of crop grown." * 



A further, perhaps even more important, ex- 

 periment has been made in connexion with the 

 power to resist the attacks of " rust," a fungous 

 disease due to the attacks of Puccinia graminis, 

 the loss caused by which is said to amount to a 

 considerable number of millions of pounds sterling 

 per annum throughout the world. 



There are some strains of wheat which resist 

 the attacks of the enemy, but unfortunately they 

 are strains which, for other reasons, are not very 

 suitable for cultivation. Mr. Biifen again attacked 

 this problem and with success. He took a form 

 which was always immune, even when grown in 

 the midst of a field of rusted plants. He took 

 another form, known as Michigan Bronze, which 

 seems never to escape the plague, and he crossed 

 the two together. Mr. Lock gives the result (p. 

 220) : 



" In the first generation every plant without 

 exception was badly rusted, but fortunately a 

 considerable number of ripe grains was obtained, 

 and these were sown to produce the second gener- 

 ation. When the plants of this generation had 

 grown up, it was observed that among a majority 

 of badly-rusted plants certain individuals stood 

 our fresh and green, being entirely free from 

 infection. On examination it was found that every 

 plant could be placed in one or other of two 

 categories either it was badly rusted or it was 



* Lock, p. 219. 



