FLOWERING PLANTS AND FERNS OF ARIZONA 75 



6. Potamogeton interior Rydb., Colo. Agr. Expt. Sta. Bui. 100: 13. 



1906. 

 Central and southern Arizona (Yavapai, Gila, Pinal, Maricopa, and 

 Pima Counties). Canada to New Mexico, Arizona, and Nevada. 

 Closely related to P. fectinatus, with which it apparently intergrades. 



7. Potamogeton foliosus Raf., Med. Repos. N. Y., ser. 2, 5: 354, 1808. 

 Coconino County to Cochise and Pima Counties, up to 8,400 feet. 



Nearly throughout North America. 



8. Potamogeton berchtoldi Fieber in Berchtold and Fieber, Potamog. 



40. 1838. 



Potamogeton pusillus, of authors. Not L., 1753. 



San Francisco Peaks, Coconino County (Thornber 2856), also 

 Young's Ranch (Lemmon in 1884). Widely distributed in North 

 America; Eurasia. 



2. ZANNICHELLIA. Horned-pondweed 



Stems filiform; leaves very narrow, opposite or whorled; flowers 

 monoecious, axillary, without perianth, the pistillate ones 2 to 5, 

 subtended by a cup-shaped involucre; staminate flowers solitary, the 

 stamen 1; ovary flask-shaped, the stigma 1, expanded. 



1. Zannichellia palustris L., Sp. PL 969. 1753. 



Coconino, Gila, Pinal, and Pima Counties, growing in ponds, ditches, 

 and slow streams. Cosmopolitan. 



3. NAIAS 



Stems slender, wholly submersed; leaves narrow, serrulate to 

 spinulose-dentate, mostly opposite or whorled; flowers unisexual, 

 axillary, solitary; staminate flowers with a spathelike involucre, the 

 stamen 1 ; pistillate flowers naked, the ovary 1, the stigmas 2 to 4. 



1. Naias marina L., Sp. PI. 1015. 1753. 



Santa Cruz River near Tucson, Pima County (Smart in 1867, 

 Pringle in 1881), Crittenden, Santa Cruz County, in a spring (Thorubt r 

 2890), 2,300 to 4,200 feet. Almost throughout North America; 

 Eurasia. 



6. JUNCAGINACEAE. Arrowgrass family 



1. TRIGLOCHIN. Arrowgrass 



Plants herbaceous, rushlike ; leaves all basal, long, narrow, semiterete, 

 with membranous sheaths; flowers in narrow spikes or spikelike 

 racemes terminating long scapes; perianth small, greenish, of 

 concave segments; stamens 3 to 6, the anthers sessile or nearly so; 

 pistil compound, of 3 to 6 carpels. 



1. Triglochin maritima L., Sp. PL 339. 1753. 



Northeastern Arizona, at Holbrook, Navajo Count v (Zuck in 1896), 

 Tuba, Coconino County {Peebles 11843), about 5,000 feet, June to 

 July. Widely distributed in the Northern Hemisphere. 



The Arizona form is var. debilis M. E. Jones. The plant sometimes 

 develops hydrocyanic acid and has been found toxic, either fresh or 



