HORDEM 



245 



long-awned. When all 3 spikelets of each group are 

 the barley is 6-rowed; when 

 only the central spikelet is 

 fertile the barley is 2-rowed. 

 In 4-rowed, or common 

 barley, all the spikelets are 

 fertile but the lateral rows 

 of the opposite sides of the 

 head overlap or intermingle 

 to form a single row. Sev- 

 eral species of Hordeum 

 are troublesome weeds. Of 

 these may be mentioned H. 

 pusillum Nutt., an annual, 

 and H. nodosum L., a per- 

 ennial, low short -awned 

 species found widely distrib- 

 uted in the United States, 

 and H. jubatum L. (squirrel- 

 tail grass) with long-a^vned 

 soft spikes, a perennial 

 found especially westward, 

 all 3 native species. Two 

 species introduced from 

 Europe, H. murinum L. and 

 H. Gussoneanum Pari., vari- 

 ously known as fox-tail and 

 wild barley, are common 

 and troublesome on the 

 Pacific coast. These are low 

 spreading annuals, the first 



., 1 <^ . . , ., , Fig. 62. Hordeum vulgare. 



With nattened spikes and cence (head), X3^; cluster of 



T . , .i , lets, and a single floret from 



Clliate glumes, the second showing the stlplform rachUla, 



fertile 



Inflores- 

 3 spike- 

 the back 

 X2. 



