MANUAL OF THE GRASSES OF THE UNITED STATES 243 



1. Triticum aestivum L. Wheat. (Fig. 475.) Culms erect, 

 freely branching at base, 60 to 100 cm tall; blades 1 to 2 cm wide; 

 spike mostly 5 to 12 cm long; internodes of rachis 3 to 6 mm long; 

 spikelets broad, glabrous or pubescent, long-awned to awnless ; glumes 

 usually strongly keeled toward one side, the keel extending into amucro, 

 the other side usually obtusely angled at apex. O (T. vulgare Vill. ; 

 T. sativum Lam.)— Commonly cultivated; fields and waste places in 

 the vicinity of cultivated fields or grain elevators, but scarcely estab- 

 lished. 



Spelt (T. spelta L.) and emmer {T. dicoccum Schrank) are sometimes 

 cultivated for the grain, used for stockfeed, and for forage. In these 

 two species the rachis breaks up, each joint bearing a spikelet which 

 remains entire, each floret permanently enclosing the grain. In 

 spelt the spikelets are somewhat distant, exposing the rachis, in emmer 

 the spikelets are closely imbricate, scarcely exposing the rachis. A 

 large number of varieties of wheat are in cultivation ; the lemmas may 

 be glabrous or pubescent, the awns long or nearly or quite wanting. 



On the basis of the number of chromosomes the wheats and their 

 allies may be divided into three groups. The group with 7 chromo- 

 somes (probably the most primitive) includes einkorn (T. monococcum 

 L.). The group with 14 chromosomes includes durum wheat (T. 

 durum Desf.), poulard wheat {T. turgidum L.), Polish wheat (T. 

 polonicum L.), and emmer (T. dicoccum Schrank). The group with 

 21 chromosomes includes spelt and the varieties of wheat commonly 

 cultivated in the United States, one series of which, with short com- 

 pact heads, is club wheat (T. compactum Host). Alaska wheat is a 

 variety of poulard wheat with branched heads. It is also known by 

 several other names, such as Egyptian, miracle, and mummy. This 

 variety is considered inferior commercially to standard varieties of 

 wheat. Stories of varieties originating from seed found with mum- 

 mies 3,000 years old have no basis in fact. 



The origin of wheat is not known as there is no native species like 

 any of the cultivated forms. Some botanists have suggested species 

 of Aegilops, and others T. dicoccoides Koern., a wild species of Pales- 

 tine, as the possible ancestor. 



41. AEGILOPS L. Goatgrass 



Spikelets 2- to 5-flowered, solitary, turgid or cylindric, placed flat- 

 wise at each joint of the rachis and fitting into it, the joints thickened 

 at the summit, the spikelets usually not reaching the one above on 

 the same side, exposing the rachis; spike usually disarticulating near 

 the base at maturity, falling entire, or finally disarticulating between 

 the spikelets. Annuals with flat blades and usually awned spikes. 

 Type species, Aegilops ovata. Name from Aegilops, an old Greek 

 name for a kind of grass. 



The species of Aegilops have been recently introduced into the 

 United States and give indications of becoming troublesome weeds. 

 At maturity the spikes fall entire, the lowest rachis joint serving as a 

 pointed callus to the 2- to several-jointed, strongly barbed fruits, 

 which work their way into the mouths and noses of grazing animals 

 and into the wool of sheep. 



Spikelets subovate; rachis not disarticulating 3. A. ovata. 



Spikelets cylindric; rachis finally disarticulating. 



Glumes with one awn 1. A. cylindrica. 



Glumes with three awns . 2. A. tritjncialis. 



