24 BULLETIN 1074, U. S. DEPARTMENT OF AGRICULTURE. 



the beginning of the Christian era called the spring wheats trimes- 

 trian, because they matured in three months from sowing. Linne 

 (lift) treated them as separate species in his Species Plantarum, 

 but combined the awned factor with the spring habit in his 

 species aestivum and .the winter habit with the awnless factor in 

 his species hybemum. Few writers have since recognized these spe- 

 cies, but the placing of both spring and winter forms of common 

 wheat in one species, Triticum vulgare, by Villars in 1787 (198) 

 has been almost universally accepted. The existence of winter and 

 spring forms has been recognized by most authors but has not re- 

 cently been used as a character for separating species or even as an 

 important character for separating varieties. The writers consider 

 these distinctions to be of less value for classification purposes than 

 several spike and kernel characters, when the whole country is con- 

 sidered, although it is a very important separation in some areas. 

 In the southern United States, both in the east and west, several 

 varieties of spring wheat are fall sown, and growers do not know 

 whether they have a spring wheat or a fall wheat. The Purplestraw 

 variety of the Southeastern States has a true spring habit, although 

 it has been grown from fall sowing in that section for more than 100 

 years. Nearly all of the varieties grown in Arizona and California 

 are spring wheats, but are fall sown. 



Hunt (123, p. 54) and others have pointed out that winter and 

 spring wheats can be changed from one form to the other. These 

 are factors which limit the value of the characters in classification. 

 To use the winter and spring habit as the first separating characters 

 also would widely separate otherwise very closely related varieties 

 and in practice would result in a double classification. 



The winter and spring habits are shown as the first characters in 

 the descriptions, as those characters are the first apparent in the 

 growth of the plant. In the key the wheats having a winter habit are 

 listed before those having a spring habit, because there are more 

 fall wheats than spring wheats and because fall wheat is of much 

 greater importance in this country than spring wheat. 



A few varieties of winter wheat are somewhat intermediate or 

 facultative in their habit of growth. This is mentioned in the de- 

 scriptions of such varieties, but in the key only the two classes are 

 recognized. The intermediate types retain their prostrate habit of 

 growth for only a short time or else they are semierect instead of 

 prostrate. Early varieties of winter wheat have a short prostrate or 

 dormant period, and when spring sown they begin heading only a few 

 weeks after the spring wheats have headed, thus giving an appear- 

 ance of intermediate habit at the later stages of growth. There are 



