CLASSIFICATION OF AMERICAN WHEAT VARIETIES. 49 



back, and the other including Sitopyrus, in which the glumes are 

 sharply keeled and in which are found all cultivated forms. This 

 bulletin is concerned only with the latter section of the genus 

 Triticum. 



There are many forms of einkorn, spelt, and emmer (including the 

 so-called " wild wheat " of Palestine) which are not cultivated in the 

 United States and, therefore, are not considered in these pages. 



Wheat is characterized as a midtall annual grass with flat blades and 

 a terminal spike. The spikelets are solitary, 1 to 5 flowered, sessile, 

 arranged alternately on the nodes of a zigzag, channeled, articulate 

 rachis ; the rachilla of the spikelets disarticulating above the glumes 

 and between the florets, or continuous ; the glumes keeled, rigid, and 

 3 to several nerved, abruptly acute or acuminate ; the lemmas keeled 

 or rounded on the back, many nerved, ending in a single tooth or 

 awn. 



The following eight divisions of wheat varieties were used by 

 Hackel (101, p. 180-187), and have been recognized by others: 



Triticum I 



sativum. 



tenax . 



Svulgare Vill Common wheat. 

 compactum Host. . .Club wheat. 

 turgidum L Poulard wheat, 

 durum Desf Durum wheat. 



dicoccum Schr Emmer. 



ispelta L Spelt. 



polonicum L Polish wheat. 



monococcum L Einkorn. 



Only three of these divisions were considered by Hackel as valid 

 and distinct species, namely, sativum, polonicum, and monococcum. 

 The other divisions he called races and subraces. The term race is 

 now more properly used for a pure line within a variety, and these 

 ranks probably would be better designated as subspecies and varieties. 

 As previously pointed out, other authors have considered these divi- 

 sions as distinct species or subspecies. The present writers have not 

 yet given sufficient study to the question of their botanical relation- 

 ships to express a positive opinion. 



In the present work it seems best to maintain these well-estab- 

 lished divisions, but at the same time to rearrange them in the order 

 of their agricultural value. The writers make no attempt to assign 

 definite rank to the different divisions, as they have not made a 

 genetic study of crosses between the different divisions nor have they 

 made an exhaustive morphological study of existing varieties or 

 strains which are of a type intermediate between any of the eight di- 

 visions. Such studies were not projected as a part of these investi- 

 gations. The divisions which have been established or recognized 

 as species or subspecies by different authors, however, may be dis- 

 tinguished by the accompanying key. 

 95339°— 22— Bull. 1074 4 



