GENERA OF GRASSES OF THE UNITED STATES. 111 
Stipa, A. elatior to Arrhenatherum, A. pennsylvanica to Trisetum, A. flavescens 
to Trisetum, A. fragilis to Gaudinia, A. spicata to Danthonia. In the Genera 
Plantarum, Linneeus cites 
Tournefort’s figure 267 
(error for 297), which is 
Avena sativa. Hence 
this is the type species. 
The most impor- 
tant species of the 
genus is Avena sativa, 
the familiar culti- 
vated oat. In many 
of. the varieties the 
awn is straight, often 
reduced, or even want- 
ing. The spikelets 
contain usually two 
florets that do not 
easily disarticulate. 
The lemmas are 
smooth or slightly 
hairy at the base, the 
apical teeth acute but 
notawned. The grain 
is permanent ly in- 
closed in the lemma 
and palea. Two other 
introduced, species are 
known as wild oats, 
because of their close 
resemblance to the 
cultivated oat. Avena 
fatua L. (fig. 58) dif- 
fers from A. sativa 
in the readily disar- 
ticulating florets, be- 
set with stiff, usually 
brown. hairs, and in 
Vic. 57.—Sphenopholig obtusata. Plant, K 4; spike- the well-developed 
let and floret, * 5. 
geniculate and twisted 
awn. <A variety of this (A. fatua glabrata Peterm.) has glabrous 
y g 5 
