238 MENDELISM 
badly rusted, but fortunately a considerable number 
of ripe grains was obtained, and these were sown 
to produce the second generation. When the plants 
of this generation had grown up it was observed 
that among a majority of badly-rusted plants certain 
individuals stood out 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 
entirely free from rust ; and the numbers of the two 
kinds of plants were as follows: 1,609 infected, 523 
immune. 
It is clear, then, that immunity and susceptibility 
to the attacks of yellow rust behave as a simple pair of 
Mendelian characters, immunity being recessive. And 
it is, therefore, possible to obtain by crossing, in three 
generations, a pure rust-free strain containing any other 
desired quality which is similarly capable of definite 
inheritance. 
BIBLIOGRAPHY. 
MENDEL, G. J.: Briefe an Carl Nageli. 
Bateson, W.: Mendel’s Principles of Heredity, 1909. 
Bateson, W.; PuNNETT, R. C.; and SaunpERs, Miss E. R.: 
Reports to the Evolution Committee of the Royal Society, 
1902-1909. 
THE JOURNAL OF GENETICS, I910— 
