FLOWERING PLANTS AXD FERNS OF ARIZONA 675 



or compound cymes, perfect, regular, the corolla gamopetalous; 

 stamens borne separately on the corolla, alternate with its lobes; 

 style 1 or none; stigmas 1 or 2; ovary superior, 1-celled; fruit a capsule. 



Key to the genera 



1, Corolla lobes with 1 or 2 conspicuous fringed glands and pits toward the base 

 of each lobe (2). 

 2. Corolla not blue, the lobes 4, each with 1 or a pair of large copiously fringed 

 glands and pits 3. Frasera. 



2. Corolla normally blue, the lobes 4 or 5, each with a pair of sparsely fringed 



nectariferous pits at base 4. Swertia. 



1. Corolla lobes without glands or pits, or these not fringed (3). 



3. Lobes of the corolla each bearing a conspicuous divaricate spur; corolla 



yellow 5. Halexia. 



3. Lobes of the corolla without spurs; corolla not yellow, but sometimes 

 ochroleucous in genus Gentiana (4). 

 4. Corolla pink, without folds or fringes, salverform; anthers becoming 



spirally twisted after anthesis 1. Cextauriu.m. 



4. Corolla not pink; anthers not becoming twisted (5). 



5. Stamens inserted in the corolla tube; corolla with folds or plaits be- 

 tween the lobes, or fringed in the throat, or the margins of the 

 lobes fringed or erose-dentate (if otherwise, then the corolla 

 ochroleucous and not more than 1 cm. long) ; style short and stout, 

 or none; inflorescence narrow and leafy, or the flowers solitary. 



2. Gentiana. 

 5. Stamens inserted in the corolla throat ; corolla without folds or fringes, 

 the lobes entire; style elongate; stigma very large, with broad 

 flattened lobes; inflorescence a loose, small-bracted panicle. 



6. Eustoma. 

 1. CENTAURIUM 



Plants annual or biennial; stems branched; calyx and the limb of 

 the corolla 4- or 5-parted, the calyx lobes keeled, the corolla salver- 

 form; stamens inserted in the throat of the corolla; stigma 2-lobed. 



The name canchalagua is sometimes used for these plants. 



Key to the species 



1. Corolla lobes 5, at least 7 mm. long, nearly as long as the tube; stems up to 

 60 cm. long, slender or stout, with more than 6 pairs of leaves; leaves 

 narrowly lanceolate or oblanceolate to broadly elliptic. 



1. C. calycosum. 



1. Corolla lobes 4 or 5, not more than 5 mm. long; stems seldom more than 



30 cm. long, slender, rarely with more than 6 pairs of leaves (2). 



2. Basal leaves not forming a rosette, not conspicuously wider than the stem 



leaves; plant normally strict, the brandies, peduncles, and leaves erect 



or narrowly ascending; corolla lobes 4 or 5 2. C. exaltatum. 



2. Basal leaves forming a rosette, conspicuously wider than the stem leaves- 

 plant rather lax, the branches, peduncles, and often the leaves ascendingl 

 spreading; corolla lobes normally 5 3. C. nudk atle # 



1. Centaurium calycosum (Buckl.) Fernald, Rhodora 10: 54. 1908. 



Erythraea calycosa Buckl., Aead. Nat. Sci. Phila. Proc. 



1862:7. 1863. 

 Centaurium arizonicum (A. Gray) Heller, Muhlenbergia 4: 86. 



1908. 



Almost throughout the State, 150 to 6,000 feet, moist soil, April 

 to October. Western Texas to southern Utah. Nevada, Arizona, and 

 northern Mexico. 



There is much variation, especially in the width of the leaves and 

 of the corolla lobes, but the writers find no satisfactory basis for the 

 distinction of varieties. 



