IMPROVEMENT OF THE POTATO. 447 



No very definite conclusions can be drawn from this one sea- 

 son's work, yet in comparing a possible inheritance of variations, 

 the difference of .81 percent in dry matter is noteworthy. It should 

 be remembered that the low protein potatoes were larger and from 

 them should have ordinarily been expected the higher dry matter. 

 The difference in total nitrogenous matter, in favor of the high 

 protein plot was 0.33 percent upon the fresh sample and 1.61 per- 

 cent upon the dried sample. The regression of each plot toward 

 the same type in percentages of dry matter and nitrogenous mate- 

 rial is great but no more than would have been expected from seed 

 propagated selections. 



Note. This experiment is being continued on a somewhat dif- 

 ferent plan. A variety of potatoes has been produced, coming from 

 a single tuber of a seedling of four years ago. With these tubers 

 two plots are being carried on, one for high and one for low nitro- 

 gen. It is expected by thus. having a check upon the effects of soil,, 

 and having to deal with an accurately estimated character, to be 

 able definitely to demonstrate whether there is inheritance of asex- 

 ual fluctuations. 



GENERAL STATEMENTS 



The improvement of our present varieties of potatoes in yield- 

 ing power, and the enhancing of particularly valuable characters 

 through breeding and selection have been shown in the foregoing 

 pages to be broad and many sided questions. They are beset with 

 difficulties such as are attendant on the improvement of no other 

 important field crop. But if the questions are difficult, some Gf them 

 are far reaching in their bearing and the subject seems alike wor- 

 thy ^the attention of the biologist seeking experimental evidence 

 concerning the meaning of sex and the inheritance of fluctuating 

 characters; and the practical breeder whose relative success in the 

 production of new varieties is measured by dollars and cents. 



The use of other tuber bearing species of Solanum as a starting 

 point for new varieties has not yet produced anything of value. 

 Hope is still entertained that 5\ Commersonii crossed, or hybrid- 

 ized, with S. tuberosum will finally produce something that is dis- 

 ease resistant and satisfactory in other respects. The present evi- 

 dence, however, seems to point towards some correlation of quality 

 with susceptibility to disease, so that definite knowledge of the 

 physiological meaning of fungus resistance is most probably the 

 key to the door we must enter. 



