578 Journal of Agricultural Research voi. xix. no. u 



although reference is made in the discussion to them and their signifi- 

 cance. 



OCCURRENCE OF H. INTERMEDIUM AND OTHER SEGREGATES IN THE 

 PROGENY OF A CROSS OF MANCHURIA AND SVANHALS BARLEYS 



The Manchuria parent in this cross is a selection of the common 6-rowed 

 barley of the northern Mississippi Valley. The side florets are fertile 

 and long-awned. The Svanhals parent is a well-known 2-rowed variety 

 with long-awned, fertile, central florets and awnless, rounded, sterile 

 lateral ones. The Manchuria is illustrated in Plate 103, C, and the 

 Svanhals in Plate 104, A. This cross was made in the Washington 

 greenhouse in the spring of 191 7, and the Fj generation was grown the 

 same season at the University of Minnesota. In the fall of 1917, 100 

 of these Fi seeds were sown in pots in the Washington greenhouse. Of 

 these, only 87 matured as Fj plants in the spring of 191 8. As soon as 

 the grain was sufficiently mature to harv^est seed was again sent to 

 Minnesota, where the F3 generation was grown. 



PHENOTYPIC CLASSES IN THE PROGENY 



The data on the F3 generation are reported in Table I, which needs con- 

 siderable explanation. In the first place, the material itself is not simple. 

 It is far from easy for a reader unfamiliar wdth barley to visualize six 

 classes of segregates. Added to this difficulty is the fact that the F3 

 classifications are of varying accuracy and are phenotypic in character. 

 The phenotypic classes of the table give a misleading impression by over- 

 emphasizing the importance of the amount of fertility present. There 

 are other characters than fertility which have much significance in the 

 genetic groups. Fertility, however, is a definite, tangible, measurable 

 condition, and the phenotypic classes founded on it are usable. In some 

 instances the phenotypic classes of the F3 generation coincide with the 

 genetic classes, while in others a phenotypic class contains more than one 

 genetic class. There is a certain amount of unavoidable confusion in 

 describing both phenotypic and genetic classes at the same time. For 

 this reason, until the genetic classes are established the plants exhibiting 

 similar phenotypic classes in their progeny are placed together and re- 

 ferred to as genetic groups. It must be remembered in studying the 

 table that the main object of the F3 classification was to determine the 

 genetic classes of the Fj generation. It is well also to recall at this time 

 that all classifications in this paper are based on the nature of the lateral 

 florets, and to avoid endless repetition the modifying adjective is fre- 

 quently omitted. In such cases the terms sterile, awn-pointed, high fer- 

 tility, etc., refer to the lateral florets only. 



Table I represents the data as taken. The first two columns of the 

 table contain the identification numbers and the description of the Fj 

 plants. In the remaining colum.ns the F3 progeny of these plants are 

 classified. These progeny fall into two major divisions, in one of which 



