40 SOUTHERN FIELD CROPS 



become " light," is due to the fact that the gluten entangles 

 and holds in the dough the bubbles of carbonic acid gas 

 formed by fermentation when yeast is added to dough. 



SPECIES AND VARIETIES 



42. Species and subspecies. The genus Triticum, to 

 which all forms of wheat belong, includes eight species or 

 subspecies. Only one of these is generally cultivated in 

 the South, namely, the winter-growing form of common 

 wheat (Triticum sativum vulgare). Spring wheat is un- 

 suited to the South. 



Macaroni wheat (Triticum durum) is adapted to a semiarid 

 climate. At least one of its varieties, under the name of Nica- 

 ragua wheat, has been successfully grown in the drier portions 

 of Texas. Macaroni wheat in that climate makes a large 

 yield of grain, which is suitable either for the manufacture of 

 macaroni or vermicelli, or for stock food. Macaroni wheat is 

 bearded. In its early growth it is more erect, and the plant is 

 less inclined to stool or tiller than common wheat. 



Other forms of wheat, not grown in the South, are the follow- 

 ing: 



Club wheat is the favorite kind in Oregon and Washington 

 (Fig. 17). 



Spelt is one form in which the chaff clings to the grains after 

 threshing. 



Emmer is useful for its resistance to drought and to rust, and is 

 especially promising as a forage plant in the semiarid Northwest. 

 It seems to be unpromising for the South because most of the 

 varieties require sowing after winter has passed. 



Poulard wheat is closely related to macaroni wheat, 



Branching wheat is so named because the head is branched. 

 In this class belongs the variety recently advertised under the 

 name of Alaska wheat, which has generally proved an inferior 

 kind. 



