1S8 hijlin lire of S('<<l Wrli/ht, <fc. on titr Potato Crop 



between A ami K be as large as 3 lbs., the actual difference between their 



yields is over fourteen times this. 



The standardised mean yields for each of the seed classes A to can 



now be irivon: 



A -IX-l E 47-5 



B 34-3 F 67-3 



C 35-7 G 40-6 



D 11-C 



and are shown diagrammatically in Fiji. 2, from which it is clear that the 

 crop increases directly willi tlie weijiht of the tuber set. If the mean is 

 taken of the values of the series A-F, we obtain the figure 41-8 for the 

 mean yield of the si.x seed classes, which corresponds very closely with 

 40-6, the standardised yield for G, the seed class where tubers are planted 

 without any conscious selection. This close approximation is of particular 

 interest, for it not only confirms the general correctness of the calcula- 

 tions, but it shows that the choice of the six seed classes A-F probably 

 covers all the chief possibilities ilUustrating the variation of yield arising 

 from seed weight differences. 



Sfandnnli-'cd yields in pounds per set 



16 

 15 

 14 

 13 

 12 

 11 

 10 



9 



8 



7^ 



6 



5 



4H 



1 ■ 



lib 



inilh 



B 



d size 



C D E F G 



Fip. -1. 



Middleton^ also found a positive correlation between yield 

 of set but only dealt with three sizes. 



The 19-21 results differ in one respect from those of 1920, where the 

 2 ozs. set produced the maximum yield, whereas in this year the yield 

 increases pari passu with the weight of the set. It may well be that the 

 latter result is the generally correct one. but the possibility must not be 



' Middleton, T. H., Guide to Experiment condvcled at Burgo)/ne\<! Farm, etc., Camb. 

 Univ. Dept. of Agiicidtiirc, 1907. 



