FLOWERING PLANTS AND FERNS OF ARIZONA 689 



Key to the species 



1. Mass of the anthers and stigma nearly globose, usually considerably surpassing 

 the hoods; column evident below the hoods but very short; hoods broadly 

 ovate or the upper part rectangular, truncate, with large winglike basal 

 auricles; leaves mostly alternate, the blades narrowly linear, elongate; 

 stems and leaves glabrous or very sparsely pubescent (2). 

 2. Anther wings entire or very nearly so; hoods (in the natural position) three- 

 fourths as high as to nearly equaling the stigma, often emarginate at 

 apex, usually without trace of an internal appendage. 



1. A. AURICULATA. 



2. Anther wings notched near the base; hoods one-half to three-fourths as 



high as the stigma, not emarginate, nearly always crested within on the 

 midnerve, the free portion of the crest appearing as a minute or elongate 



subulate horn _ 2. A. rusbyi. 



1. Mass of the anthers and stigma longer than wide, usually very slightly surpass- 

 ing the hoods; column concealed by the insertions of the hoods; hoods 

 oblong-lanceolate, obtuse, with small, concealed, basal auricles; leaves 

 often opposite or nearly so, the blades lanceolate, elliptic, or oblong; stems 

 and leaves tomentulose (3) . 



3. Hoods auricled at base, otherwise entire 3. A. viridiflora. 



3. Hoods 2-parted, the divisions lanceolate 4. A. bifida. 



1. Acerates auriculata Engelm. in Torr., U. S. and Mex. Bound. Bot. 



' 160. 1859. 

 Pinal Mountains, Gila County {King and Belden 2427), probably 

 elsewhere in the State. Nebraska to Texas and Arizona. 



2. Acerates rusbyi Vail, Torrey Bot. Club Bui. 25: 37. 1898. 

 Navajo and Coconino Counties to Cochise and Pima Counties, 



4,000 to 7,000 feet, commonly in open pine forests, June to September, 

 type from Oak Creek, Yavapai County (Rusby in 1883) . Known only 

 from Arizona. 



This species has the hoods with a minute to well-developed hornlike 

 appendage within, thus breaking down the only technical character 

 separating Acerates from Asclepias. Without flowers it is indistin- 

 guishable from A. auriculata. 



3. Acerates viridiflora (Raf.) Eaton, Man. Bot. ed. 5, 90. 1829. 



Asclepias viridiflora Raf., Med. Repos. N. Y. 5: 360. 1808. 



Near Flagstaff (Coconino County) and Prescott (Yavapai County), 

 5,400 to 7,000 feet, June and July. Massachusetts to Saskatchewan, 

 south to Florida and Arizona. 



The Arizona form is var. lanceolata (Ives) Gray (A. ivesii (Britton) 

 Woot. and Standi.) with lanceolate leaves, these narrower than in 

 typical A. viridiflora. 



4. Acerates bifida Rusby ex A. Gray, Amer. Acad. Arts and Sci. Proc. 



20: 296. 1885. 

 Known only by the type collection, presumably in Yavapai County, 

 Arizona, but a letter from Rusby to Gray, filed with the type in the 

 Gray Herbarium, leaves it wholly uncertain where the type was 

 actually collected. 



4. ASCLEPIAS. Milkweed 



Stems herbaceous or woody below, commonly erect, never twining, 

 the sap usually milky; leaves commonly opposite or whorled, some- 

 times early deciduous; inflorescences terminal or lateral, usually 

 many-flowered; corolla lobes commonly reflexed in anthesis; hoods 



