2(> 



world. Manifestly a complete treatment of the subject can not be 

 presented in the present state of om' knowledge, since wheat varieties 

 and their adaptations have not been thoroughlj' studied in all parts of 

 the world. Nevertheless, considerable investigation has been made in 

 this line, and the future promises still more. Such studies are exceed- 

 ing-ly interesting, and form an absolutely necessary part of the basis 

 for rational wheat improvement. 



CHARACTERISTICS OF BOTANIC GROUPS OF WHEAT. 



The cultivated varieties of Triticum., according to Kornicke and 

 Werner,^ whose classification will in the main be followed in this bul- 

 letin, may be grouped into eight species and subspecies, as follows: 

 Triticuin mdgare, T. conqmctitm^ T. durum, T. turgldimi, T. poloni- 

 cimi., T. Kpdta., T. dicoccnim^ and T. monococciiiii. Only T. vulgare^ 

 T. polonicum, and T. monococcum are considered to be good species- in 

 all classifications. The other five are generally considered as subspe- 

 cies of T. vidgare^ though T. coriipacturu is sometimes not even ele- 

 vated to that rank. In this bulletin they will all be referred to as 

 though they were distinct species. The chief characters of these 

 groups of wheats will now be described, with special reference to their 

 importance in wheat improvement. 



COMMON BREAD WHEATS [TrUicum vulgare). 



This is of course the most valuable and widely distributed group of 

 wheats in the world, and is represented l)y a greater number of varie- 

 ties than all other species taken together. Nevertheless a number of 

 veiy important qualities can be found only among varieties of the 

 other species. 



The characters of this group, both l^otanical and agricultural, are 

 well known. The heads are long in proportion to thickness, as com- 

 pared with those of some other groups. The}^ are broader in the plane 

 of the rows of spikelets, as a rule, and narrower on the sides of the 

 fui-row between the rows; taper toward the apex, but may be very 

 blunt or even thicker above; are usually looseh^ formed comparatively^ 

 bearded or bald, and usually possess smooth chaff, but may Ix^ velvety. 

 The spikelets, or meshes, as they are popularly called, generally con- 

 tain three grains, but sometimes two and rarely four. The empty 

 glumes or outer chaff of the spikelets are slightly keeled above and 

 merely arched below. The -stem of th(^ plant is usually hollow, l)ut 

 occasionally somewhat pithy within and varies greatly in strength and 

 height in different varieties. The leaves also vary in character, but 

 are rarel}^ as wide as those of the durum and poulard groups, and are 

 velvety in only a few varieties. 



1 Kornicke, Fr., and Werner, H. Handbuch des Getreidebaues, 1885. 



