28o PLANT-BREEDING 



have been studied from this point of view. In barley, one of 

 the main characters and one which has been already alluded 

 to is found in the hairiness of the scales, bristles, and other 

 parts of the spikelets and flowers. In some cases the hairs 

 are smooth and pressed against the scales, in others they 

 are stiff and spreading. Crisp and woolly hairs arc, as a 

 rule, to be considered as indicating the most valuable types. 

 Experience has taught that in this simple way it is possible 

 to select in each variety the elementary form that will prob- 

 ably be the best yielder. The midveins of the outer scales 

 afford still further marks. In some cases they are smooth, 

 in others armed with small but sharp teeth. Even these 

 differences are constant in pure cultures, and indicative of 

 correlated yiclchng quahties. 



The same laws of correlation have been observed with 

 other agricultural plants. Prominent amongst all are the 

 forage crops of the large family of the leguminous plants. 

 Here the differences between the numerous elementary 

 forms within the botanical species are not so very small 

 and so difficult to realize as in the cereals. Peas and vetches 

 have been studied in the first place, but clovers, wild species 

 of sweet-peas, and several other forms, whose culture had as 

 yet hardly been profitable, have also afforded notable results. 

 For peas the correlations have been studied by Mr. Tedin, 

 who has published liis results in tables, giving the average 

 weight of the seeds, their number in the pods, and their 

 total number on the individual plants, in combination with 

 other valuable qualities. On the ground of this system he 

 has been able to distinguish 500 different kinds of peas, 

 which have proven constant in his pedigree cultures, and 

 among which some 40 could be selected as evidently ex- 

 celHng the ordinary varieties out of wliich they had been 

 isolated. 



In the same way some 75 new and constant types of 



