122 A MANUAL OF MENDELISM 



By the earlier method and the assistance of natiire 

 a number of good yielding varieties had been identified 

 at Svalof before the end of the nineteenth century, 

 nearly all of which were directly descended from imported 

 varieties. The action of nature had been to indicate 

 and sometimes kill off plants which did not withstand 

 rust and the Swedish winter or were liable to lodg- 

 ing ; and such plants as nature failed to kill were 

 picked out by hand. Thus, by the weaker individuals 

 being weeded out, the productivity of a variety was 

 increased. It will be well to compare the yields of 

 some of the varieties so selected with that of a native 

 variety and see, at the same time, how certain varieties 

 are affected by one of the causes contributing to depress 

 the yield. The comparison is made with the yields of 

 the years 1907 to 1912. These are given in kilogrammes 

 to the hectare, and, for ease in comparison, are reduced 

 to a basis in which the native variety, Sammets wheat, 

 stands at 100. 



Variety Kilogrammes per hectare 



S 0-0 



1907 1908 1909 1910 1911 1912 g 



I PS 1^ 



Sammets Wheat 2370 3310 2370 4140 3930 3440 3260 100 



Strubes Square- 

 head . . 25401 35402 760» 5380 4490^ 2710^ 3220 98- 8 



Stand Up . . 3170» 3660^ 950' 5360 4740 3370' 3550 108-9 



Extra Squarehead 2460 4030 2640 4500 — — 3647 111-9 



Danish Bore Wheat 2760 3910 2900 4580 4210 4150 3752 115-1 



Renodland Square- 

 head . . 2740 3580 3420 5220 4590 4180 3955 121-3 



Grenadier II . 3110 4240^ 2620* 4950 5110 3720^ 3959 121-4 



1 Slightly damaged by winter. * Fairly strongly damaged. 



' Very strongly damaged. 



An examination of the foot-notes will show that, while 

 most of these varieties vield well after a mild winter — 



