FLOWERING PLANTS AND FERNS OF ARIZONA 285 



or salverform limb, the lower part of the tube persistent, becoming 

 hardened and closely investing the fruit; ovary 1 -celled, appearing 

 inferior, but technically superior; fruit usually ribbed, grooved, 

 or winged. 



Key to the genera 



1. Stigma narrowly linear, this and the stamens included in the perianth tube; 

 cotyledon one, by abortion (2). 

 2. Limb of the perianth 5-lobed; wings of the fruit thickish, opaque, interrupted 

 above and below the body of the fruit 10. Abronia. 



2. Limb of the perianth 4- or 5-lobed; wings of the fruit thin, nearly transparent, 



conspicuously reticulate- veined, continuous around the body of the 



fruit 11. Tripterocalyx. 



1. Stigma globose or hemispheric; cotyledons 2 (3). 



3. Wings of the fruit 3 to 5, conspicuous, scarious (4). 



4. Free portion of the perianth tubular-funnelform; stamens 5 or 6, attached 

 to the lower part of the perianth tube 1. Selinocarpus. 



4. Free portion of the perianth broadly campanulate; stamens 2 or 3, free 



from the perianth 2. Ammocodon. 



3. Wings of the fruit none or coriaceous, sometimes (in genus Boerhaavia), the 

 angles narrowly winglike, subscarious (5). 



5. Fruit strongly compressed, oval or obovate in outline, the (usually dentate) 



margins commonly strongly inflexed over the dorsal (outer) face. 



6. Allioxia. 

 5. Fruit not compressed, terete or angled, without inflexed, dentate margins 

 (6). 

 6. Floral bracts more or less united into a calyxlike involucre: stamens 

 and pistil more or less exserted (7) . 

 7. Fruits not strongly 5-angled (sometimes noticeably o-ribbed), 

 usually not constricted at base; involucre in fruit scarcely en- 

 larged, remaining leaflike in texture 4. Mirabilis. 



7. Fruits strongly 5-angled longitudinally, constricted at base; in- 



volucre in fruit greatly enlarged, thin, conspicuously veined. 



5. Oxtbaphus. 

 6. Floral bracts separate, remaining small (8) . 



8. Flowers solitary, axillary; bracts persistent 3. Acleisanthes. 



8. Flowers in umbels, cymes, or racemes; bracts usually soon deciduous 



(9). 

 9. Fruits with not more than 5 angles or ribs; free portion of the 

 perianth campanulate to nearly rotate, with scarcely any tube. 



7. Boerhaavia. 

 9. Fruits 10-ribbed; free portion of the perianth funnelform, with a 

 distinct tube (10). 

 10. Fruits narrowly clavate, wingless, conspicuously beset with 



wartlike, stipitate glands 8. Commicarpus. 



10. Fruits biturbinate, with a rigid, horizontal, median annular 

 wing, glandless _ 9. Anulocaulis. 



1. SELINOCARPUS 



Plant perennial; stems low, diffusely branched; leaves opposite, 

 thickish, with ovate blades; flowers few, axillary and solitary, or in 

 short-stalked terminal leafy clusters; free portion of the perianth 3 

 cm. long, or longer; stamens 5 or 6; fruit conspicuously winged. 



*1. Selinocarpus diffusus A. Gray, Amer. Jour. Sci. ser. 2, 15: 262. 

 1853. 

 Not known definitely to occur in Arizona but has been collected 

 near St. George, Utah. Western Texas to southern Nevada. 



2. AMMOCODON 



Plant perennial, with the habit of Selinocarpus; leaves opposite, 

 with broadly ovate blades; flowers several or numerous, in simple or 



