404 



BULLETIN No. 127. 



[August, 



Marek's work stimulated Wollny (113) to continue his inves- 

 tigations. In this later work his former conclusions were modified. 

 He found that in the majority of cases the progeny of tubers hav- 

 ing a high specific gravity were of a slightly higher specific gravity 

 than those descended from tubers of a low specific gravity. He be- 

 lieves, however, that it is very doubtful whether any effectual im- 

 provement of the value or yield of a variety could take place 

 through selection of tubers of high specific gravity. Further in 

 Marek's* final report, he admits practically the same thing. 



Girard (45, 46) reached the same conclusion with regard to 

 specific gravity with the use of five varieties, but highly recommends 

 the selection of high-yielding plants in the field as means of keeping 

 up the yield of the variety. 



Hebert found no transmission of high specific gravity with a 

 large number of experiments with Richter's Emperator. 



Wohltmann's (107) and Thiele's (96) results showed that the 

 hereditary transmission of starch content had not been clearly 

 proved. 



Goff (49), in experiments begun in New York in 1884 and 

 continued four seasons, found that the yield of tubers from pro- 

 ductive hills was greater than that from unproductive hills, but that 

 the difference in yield between different rows of selected tubers was 

 often as great as the difference between the two selections, and 

 even this might be entirely due to the fact that the plantings were 

 all made from single eye pieces, which were larger in those from 

 productive hills. Realizing the error in planting different weight 

 seed pieces, he (50) began again in 1899. This time the same 

 number of tubers and of cuttings were taken and the combined 

 weights of each selection were made the same. The collected re- 

 sults were as follows : 



*Marek, E., Deut. landw. Presse 1895:274. 



