34§ miscellaneous. [1878. 



Mr. Torbitt's Experiments on the Potato-Disease. 



[Mr. James Torbitt, of Belfast, has been engaged for the 

 last twelve years in the difficult undertaking, in which he has 

 been to a large extent successful, of raising fungus-proof 

 varieties of the potato. My father felt great interest in Mr. 

 Torbitt's work, and corresponded with him from 1876 on- 

 wards. The following letter, giving a clear account of Mr. 

 Torbitt's method and of my father's opinion of the probability 

 of its success, was written with the idea that Government 

 aid for the work might possibly be obtainable :] 



C. Darwin to T. H. Farrer. 



Down, March 2, 1878. 



My DEAR Farrer, — Mr. Torbitt's plan of overcoming the 

 potato-disease seems to me by far the best which has ever 

 been suggested. It consists, as you know from his printed 

 letter, of rearing a vast number of seedlings from cross-fertil- 

 ised parents, exposing them to infection, ruthlessly destroying 

 all that suffer, saving those which resist best, and repeating 

 the process in successive seminal generations. My belief in 

 the probability of good results from this process rests on the 

 fact of all characters whatever occasionally varying. It is 

 known, for instance, that certain species and varieties of the 

 vine resist phylloxera better than others. Andrew Knight 

 found one variety or species of the apple which was not in 

 the least attacked by coccus, and another variety has been 

 observed in South Australia. Certain varieties of the peach 

 resist mildew, and several other such cases could be given. 

 Therefore there is no great improbability in a new variety of 

 potato arising which would resist the fungus completely, or 

 at least much better than any existing variety. With respect 

 to the cross-fertilisation of two distinct seedling plants, it has 

 been ascertained that the offspring thus raised inherit much 



