OCCURRENCE OF THE FIXED INTERMEDIATE, HOR- 

 DEUM INTERMEDIUM HAXTONI, IN CROSSES BE- 

 TWEEN H. VULGARE PALLIDUM AND H. DISTICHON 

 PALMELLA^ 



By Harry V. Harlan, Agronomist, Office of Cereal Investigations, Bureau of Plant 

 Industry, United States Department of Agriculture, and H. K. Hayes, Head of Section 

 of Plant Breeding, Division of Agronomy and Farm, Managem.ent, Minnesota Agricul- 

 tural Experiment Station 



INTRODUCTION 



The cultivated barleys belong to the genus Hordeum and are charac- 

 terized by the presence of three single-flowered spikelets at each node of 

 the rachis. The floret of the central spikelet develops a normal kernel in 

 all forms of barley. The lateral florets, on the other hand, may develop 

 normal or undersized kernels or may be sterile or even abortive. In 

 classifying the varieties, Harlan (2)^ recognized four species, basing them 

 on the degree of fertility in the lateral florets. Varieties of three of these 

 species are concerned in the data presented herein. In all varieties 

 mentioned, the central florets are long-awned. The 6-rowed parents in 

 all hybrids belonged to the botanical variety H. vulgare pallidum, and 

 include Manchuria, S. P. I. No. 20375,Sex-radigt, Odessa, Reid Triumph, 

 Surprise, and a hybrid 6-rowed X 2-rowed barley. The lateral as well as 

 the central florets of these varieties are long-awned and produce well- 

 developed kernels. 



The 2-rowed parents all belong to the variety H. distichon palmella. 

 The central florets are long-awned, while the lateral ones are awnless with 

 rounded tips and are sterile. Of the varieties mentioned in the text, 

 Svanhals, Garton, and Primus belong to this group. The intermediates 

 are products of hybridization, and the selections are unnamed. All, how- 

 ever, belong to the botanical variety H. intermedium haxtoni. In these 

 the central florets are long-awned and produce normal kernels, while 

 the lateral florets are awnless, as in the 2-rowed barleys, but fertile, pro- 

 ducing undersized but viable kernels. The percentage of fertility in 

 these spikelets is not so high as in the 6-rowed, but neither are they in- 

 fertile, as are the 2-rowed. This form, obviously intermediate in char- 

 acter between the 6-rowed and 2-rowed barleys, has proved to be 

 constant and is as distinct in its genetic behavior as either the 6-rowed or 

 the 2-rowed forms. 



The history of the intermediate barleys is very interesting, but not 

 always clear. The first recorded observation found is that of John Hax- 

 ton (5) in Scotland. In Morton's Cyclopedia of Agriculture of 1851 he 

 mentions having observed such a plant in a field of " Bere." At the time 



• This paper is based upon experiments conducted cooperatively by the Ofi&ce of Cereal Investigations, 

 Bureau of Plant Industry, United States Department of Agriculture, and the Minnesota Agricultural 

 Experiment Station. 



' Reference is made by number (italic) to " Literature cited," pp. 590-591. 



Journal of Agricultural Research, Vol. XIX, No. 11 



Washington, D. C. Sept. i, 1920 



ux I Key No. G-204 



(575) 



