164 



HORDEAE 



Culms iriungular; involucral bract 1, seem- 

 ing to be a prolongation of the culm. 



Invdhicral bract short, about 1 inch long 

 or less, barely exceeding the spike- 

 lets which are generally 4 to 6 and 

 crowded: leaves about one-fifth the 

 length of the culm. 



Involucral bract 1 1-2 to 4 Inches long, 

 much exceeding the spikelets which 

 are few in number, frequently only 1, 

 and small; leaves half as long to al- 

 n:ost as long as the culms. 



Involucral . bracts of several flat leaves which 

 much exceed the compound umbellate in- 

 florescence. 

 Culms uiangular; spikelets large, 10 to 20 

 mm. long, light yellowish brown; inflor- 

 escence a simple umbel or in your.g plants 

 capitate. 



Culms terete; spikelets small, 2 to 7 mm. 

 long, greenish; inflorescence a once t 

 twice compound umbellate cluster vith 

 unequal and numerous rnys. 

 Stylo branches 2; akenes rounded on llie 

 back; inflorescence twice compound; 

 spikelets not capitate. ' 



Style branches 3 ; akenes angled on the 

 back: inflorescence generally once 

 (so::, climes twice) compound spike- 

 Itit i I i.nsely capitate at the ends of the 

 rayiets. 



2. S. olneyi. 



S. americanus. 



4. S. campestris. 



S. microcarpus. 



S. atroiurens. 



1. Scirpus paucifljri'S I.ightf. Prohabh- not uncommon in 

 the mountains. Only one collection seen. In wet soil. 



2. Scirpus olneyi A. Giay. In wet alkaline soil beside 

 springs, water holes and streams; in the Upper Sonoran Zone. 



3. Scirpus americanus Pers. In water soaked soils at 

 various levels throuohout the State; mainly in the Soncran Zones. 



4. Scirpus campestris Britton. {Scirpus maritimus of 

 various authors not of Linnaeus.) In wet soil in the warmer parts 

 of the State; in the Sonoran Zones. 



5. Scirpus occidentalis (S. Wats.) Chase. Bull Rush. 

 In wet and boggy soil beside streams, water holes, cienagas, etc., 

 mostly in the Sonoran Zones. 



6. Scirpus microcarpus Presl. Beside streams and ditches 

 and in cienagas in the mountains ; in the Transition Zone. 



7. Scirpus atrovirens Muhl. Collected but once in New- 

 Mexico near Pecos in (h(> I'!;) er Sonoran Zone. 



