180 orton: pathology of solanum tuberosum 



that the older data (which were reduced by the present system of 

 computation long before the inconsistencies among the various 

 sets of the present observations were eliminated) are in close 

 agreement with the present results. 



PHYTOPATHOLOGY. — Environmental influences in the pathol- 

 ogy of Solanum tuberosum.^ W. A. Orton, Bureau of Plant 

 Industry. 



The health and vigor of plants is largely dependent on their 

 adaptation to their environment. Each species has its optimum 

 requirements as to temperature, moisture, light and substratum, 

 variations from which result in failure of the plant to reach a 

 normal or maximum development and predispose it to disease. 



Under certain environmental conditions, for example, the 

 plant becomes more susceptible to the attacks of parasites, either 

 because the germination and development of the parasite is fav- 

 ored or because the weakened host has lost its natural resistance. 

 Another type of disease is not associated with any parasites, but 

 comes from some perversion or loss of physiological functions, 

 which seems also, in the last analysis, to be attributable to defects 

 in the environment. 



It is to be expected that the most favorable climate for any 

 plant will be that of its nativity, to which it has become adapted 

 in the course of its evolution. Certainly the students of crop 

 plants should consider first the natural adaptations of their 

 plant in the land of its origin, and next any modification that 

 may have resulted from subsequent culture in other countries. 



The native habitat of Solanum tuberosum, the progenitor of 

 our potato, is believed to be in southern Chile, where it was found 

 growing wild by the early explorers and where it still occurs. 

 Darwin, in the Voyage of the Beagle describes his experiences on 

 the Island of Chiloe, where ' ' the wild potato grows .... 

 in great abundance, on the sandy, shelly soil near the sea beach." 



' Address of retiring President, Botanical Society of Washington, February 25, 

 1913. 



