Triticum. . . 
sativum 
CLASSinCATIOI^ OF AIMEEICAN WHEAT YAEIETIES. 49 
back, and the other including Sitopyrus, in which the ghimes 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: 
ivulgare Vill Common vrheat. 
compactum Host. . .Club wheat, 
turgidum L Poulard wheat, 
dui'um Desf Durum wheat. 
dicoccum Schr Emmer. 
spelta 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^ polonicuin^ 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 ranl^ 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 
