242 A TEXT-BOOK OF GRASSES 



ting into 2 parts, the spikelets much compressed, 2-flowered but 

 usually 1-seeded. 



266. Classification of the wheats. — The cultivated 

 forms of the genus Triticum may be divided into 2 series: 

 (1) The spelt wheats, in which the axis disarticulates and 

 the grains are permanently inclosed in the spikelets. This 

 group includes spelt (7". spelta L.), emmer (T. dicoccum 

 Schrank) and einkom (T. monococcum L.), the latter, 

 grown to a limited extent in certain parts of Europe, being 

 distinguished by the 1-a^vned spikelets with usually only 

 1 grain. (2) The naked wheats, in which the axis is 

 entire and the grains not permanently inclosed by the 

 spikelets. In these the grain can be separated from the 

 chaff by threshing. The group includes Polish wheat 

 (T. polonicum L. ), durum wheat (7". durum Desf.), Eng- 

 lish wheat (T. turgidum L.) and the numerous varieties of 

 wheat grown in America, T. oestivum L., T. vulgare Vill., 

 and T. sativum Lam. (See Jessen, Deutschlands Graser 

 191. 1863.) 



Hackel's classification. — Hackel divides the cultivated 

 wheats into 3 species on more technical botanical char- 

 acters: 



A. Terminal spikelet aborted, often scarcely 

 visible. Palea faUing into 2 parts at maturity. 



Lateral teeth of glumes acute 1. T. monococ- 



AA. Terminal spikelets developed; palea remaining [cum. 



entire; lateral teeth of the glumes obtuse. 

 B. Glumes shorter than any of the lemmas, 



chartaceous; palea as long as lemmas 2. T. sativum. 



BB. Glumes as long as or longer than any of the 

 lemmas, papery, lanceolate; palea of the 

 lowest flower half as long as its lemma 3. T. polonicum. 



Triticum sativum, (the equivalent of T. oestivum) he 

 divides as follows into 3 groups which he calls races: 



