BOOT CHOPS. 55 



soni has been cultivated in its native country (Chili) for 

 some time. Experiments have been made in England to 

 introduce some of these species and to cross them with 

 the ordinary potato, in order to obtain a product which 

 might possibly not be susceptible to the potato disease." 

 According to Mr. J. G. Baker, F.E.S., Solanum Maglia 

 and 8. Commersoni would suit the humid climates of 

 Great Britain and Ireland. They are both great disease- 

 resisters. 



Nearly all the old varieties of cultivated potatoes either 

 fall a ready prey to the attacks of Peronospora, or have 

 become so unfruitful as to be scarcely worth planting. 

 The variety known as the " champion " " has lost much of 

 its productiveness." " The ' regent ' is worn out ; and 

 many of the newer seedlings of that class, although good 

 croppers, are at the mercy of a moist season." Mr. Baker 

 states that Solanum tubei'osum " in its present tuber- 

 bearing state is in a disorganized, unhealthy condition, a 

 fitting subject for the attacks of fungi and aphides." 

 Other observers say " it is impossible to over-cultivate any 

 plant." In our opinion, this is a mistake, for over- 

 manuring with the favourite kainit or potash manures 

 generally has a tendency to favour the development and 

 growth of Peronospora infestans and similar fungi 

 {Chemical Neivs, vol. 53, p. 255). 



Potato-growers should try to produce by crossing, etc., 

 a disease-proof potato. The late Mr. Darwin was greatly 

 interested in Torbitt's experiments " of raising fungus- 

 proof varieties of the potato." He describes Torbitt's 

 method of procedure ^ in the following words : " It con- 

 sists of rearing a vast number of seedlings from cross- 



' Life and Letters of Charles Darwin, Yol. iii. p. 348. 



