FLOWERING PLANTS AND FERNS OF ARIZONA 179 



Water-stargrass. This plant sometimes grows so profusely in the 

 canals and ditches as to obstruct the flow of water, causing considera- 

 ble expense for removal. It is strictly aquatic. 



2. Heteranthera limosa (Swartz) Willd., Neue Schr. Gesell. Naturf. 

 Freund. Berlin 3: 439. 1801. 



Pontederia limosa Swartz, Prodr. Veg. Ind. Occ. 57. 1788. 



San Bernardino Ranch, Cochise County, 4,000 feet (Mearns 609). 

 Virginia to South Dakota, southward to Florida, Louisiana, and 

 southeastern Arizona; tropical America. 



16. JUNCACEAE. Rush family 



Plants herbaceous, mostly perennial, grasslike, with narrow sheath- 

 ing leaves; perianth regular, the 6 divisions glumelike; stamens 3 to 6; 

 ovary 1-celled or 3-celled; stigmas 3; fruit a' capsule. 



Key to the genera 



1. Plants glabrous; leaf sheaths open; ovary usually more or less 3-celled; ovules 

 many, attached to the axis or walls of the ovary (the placentas axial or 

 parietal) 1. Juncus . 



1. Plants with long soft hairs (these sometimes very few); leaf sheaths closed; 

 ovary 1-celled; ovules 3, attached to the base of the ovary (the placentas 

 basal) 2. Luzula. 



1. JUNCUS. Rush 

 Contributed by F. J. Hermann 



Principally perennial, grasslike herbs of wet habitats, with glabrous, 

 pithy or hollow, usually simple, stems; leaves glabrous, the sheaths 

 open, the blades terete or flattened, sometimes wanting; inflorescence 

 cymose, paniculate, or glomerate, often unilateral; flowers small, 

 greenish or brownish, glumaceous; capsule 3-celled with a central 

 placenta, or 1-celled with parietal placentas; seeds numerous, retic- 

 ulate or ribbed, sometimes appendaged. 



Plants bearing mature fruit and the persistent perianth and stamens 

 are essential for identification of most of the species in this genus. 

 Occasionally Juncus saximontanus is sufficiently abundant in moist 

 meadows to become a principal ingredient of the "grasses" cut for 

 hay, and other species may be locally so plentiful as to have an 

 appreciable forage value, but otherwise the rushes of Arizona are of 

 no economic importance. 



Key to the species 



1. Inflorescence appearing lateral, the involucral bract terete, stiffly erect, 

 resembling a continuation of the stem; leaves all basal or nearly so, never 

 septate (2). 

 2. Flowers 1 to 3 (rarely 4 or 5); seeds conspicuously tailed; low alpine plant, 



5 to 20 cm. high 1. J. drummoxdii. 



2. Flowers many; seeds not tailed; plants usually taller, of the Sonoran and 



Transition Zones (3). 



3. Stems relatively slender, not very rigid; inflorescence not glomerate: each 



flower with 2 bracteoles at base in addition to the bract let at base of 



the pedicel (4). 



4. Stems compressed; leaf blades usually present ; perianth usually greenish 



or straw-colored 1 4. J. mex canus. 



