80 



ing, was extremely susceptible to the above disease and was quite useless for 

 commercial purposes. 



Another pedigree sort, taken from the Extra Squarehead autumn wheat 

 proved considerably more winter hardy than the latter, but was found to be 

 weaker in the straw. An advance had thus been made in one direction at the 

 expense of another. Certain selections taken from Selected (Renodlad) Square- 

 head have excelled it slightly in yield, but also seem less strong in the 

 straw. (See F. 25). 



The difficulties associated with line-breeding work now seem easy of 

 explanation. The various strains or biotypes found in old races are the 

 result of a planless crossing in nature and as such are comparable with those 

 which were produced artificially at Svalof before the combinations idea had 

 been developed, and with the results already indicated. In the light of the 

 above idea, it seems clear that the prospects of success are infinitely greater 

 where crossing work is prosecuted systematically and with an idea of effecting 

 some definite combination of desirable characters. The sorts to be crossed 

 must also be especially chosen and a careful exploitation made of all com- 

 binations which approximate the desired end. In accordance with the above 

 principle, artificial crossing work has come to occupy a front place in the 

 general system of cereal breeding at Svalof. 



While some progress has been made in isolating from old varieties of 

 autumn wheat, strains which are more winter hardy than the latter, yet a 

 strain combining a sufficient degree of hardiness with the productivity of the 

 best yielder has not yet been obtained from this source. Artificial crossing 

 has therefore been resorted to and has resulted in very evident progress, the 

 sort known as Extra Squarehead No. II standing as the most conspicuous 

 monument to the efforts put forth in this direction. Thus far no sort has 

 been obtained which combines the maximum yielding power of the highest 

 yielder and the maximum strength of straw of the stiffest sort with the degree 

 of hardiness of the common Swedish sorts, although progress is gradually 

 being made in this direction by continued cross-breeding work. 



Efforts to find in old races, strains combining early maturity with high 

 yield, while by no means fruitless, have not fulfilled earlier expectations. 

 The high yielding though relatively early maturing Gold Rain oats (isolated 

 from the old Probtdier variety) is perhaps the best example of progress in 

 this direction. Notwithstanding all efforts which have been made however, 

 to obtain still earlier sorts of equal yielding capacity by a further exploitation 

 of the above old variety, not a single instance of real progress is on record. 

 True, somewhat earlier sorts have been discovered, but these have proven 

 defective in certain other essential qualities and have thus marked no real 

 advance. Thus the sort 0336 (40, p. 14), though somewhat earlier than Gold 

 Rain, was found to be weak in the straw and was consequently abandoned. 

 Artificial crossing between early sorts is therefore being prosecuted as a 

 means of obtaining that which selection failed to give. 



In the prosecution of crossing work due regard is taken of the fact that 

 sorts which are morphologically alike may be constitutionally different, and 

 may when crossed, produce gradations which excell both parents in regard to 

 certain practical qualities. Thus "When the specific aim is to obtain a 



