iQoS.] IMPROVEMENT OF THE POTATO. 379 



adenium were quite resistant to late blight, while S. stoloniferum 

 was not. In his later (93) report of 1905, they all showed a high 

 percentage of infection. None of these species or varieties gave 

 marketable tubers in his tests, but they had hardly been cultivated 

 by him long enough to have become adapted to Vermont conditions. 

 De Candolle (22 p. 49) mentions that S. verrucosum is not dis- 

 ease resistant. 



It seems unlikely from past results, that there will be any great 

 progress made through straight selections of other species, if we 

 except S. Commersonii. This species has been thus far very unsat- 

 isfactory in the United States, but there is in it still cause for ex- 

 periment. It is very variable in its habits of growth, length of 

 stolons, shape of tubers and other important characters ; hence there 

 may in time be some promising strains isolated. Until we have 

 such strains established, there wkl probably be little good from 

 hybridizing mediocre elementary species with the common potato, 

 for the hybridization is effected with difficulty. 



For two seasons the writer has had under observation some 

 plants grown from tubers of Labergerie's stock imported by J. J. H. 

 Gregory and son, Marblehead, Massachusetts. Phytophthora in- 

 festans has not been troublesome during either of these seasons; 

 hence, no data have been obtained regarding the comparative re- 

 sistance of the plants to the fungus. I am compelled to state, how- 

 ever, that in no character off leaf, stem, flower or tuber, is 

 the plant different from common purple tubered varieties of S. tu- 

 berosum. Either there has been some mistake in Labergerie's 

 seemingly careful work, and there has been a mixture with tubers 

 of S. tuberosum; or we must conclude that there have been bud 

 mutations in at least five or six characters of S. Cornmersonii, giving 

 a plant indistinguishable from S. tuberosum. The truth of the latter 

 conclusion would give us a unique phenomenon that is of extreme 

 importance to science, and the case must be confirmed before it is 

 accepted as a fact. 



Our plants have flowered freely, but viable pollen has been pro- 

 duced in extremely small quantities. Numerous attempts at hybrid- 

 izing with S. tuberosum have all failed. 



