848 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



6. CRUSEA 



Plants small, annual; stems slender, erect or ascending, simple or 

 sparingly branched; leaf blades oblong-lanceolate to subulate; flowers 

 small, in terminal or axillary glomerules; calyx lobes 2 to 4, often con- 

 spicuously unequal; corolla white or purple, salverform or nearly so; 

 fruit of 2 to 4 obovoid or globose carpels, these separating at maturity 

 from the persistent axis. 



Key to the species 



1. Herbage sparsely hirsute; leaf blades oblong-lanceolate, up to 10 mm. wide, 

 conspicuously several- veined; glomerules of flowers mostly solitary at the 

 ends of the main stem and branches, capitate; calyx lobes attenuate- 

 subulate, more or less unequal in length but not conspicuously different in 

 texture; corolla rose purple 1. C. wrightii. 



1. Herbage glabrous or (commonly) sparsely hispidulous; leaf blades linear- 

 lanceolate or subulate, not more than 3 mm. wide, with only the midvein 

 apparent; glomerules several, axillary and terminal; calyx lobes very 

 unequal, some of them lanceolate and foliaceous, the others reduced to 

 setaceous, scarious teeth; corolla whitish 2. C. subulata. 



1. Crusea wrightii A. Gray, PL Wright. 2: 68. 1853. 



Huachuca Mountains, Cochise County {Lemmon 2724), Sycamore 

 Canyon near Ruby, Santa Cruz County, 3,600 feet (Kearney and 

 Peebles 14447), August and September. Southeastern Arizona and 

 northern Mexico. 



2. Crusea subulata (Pavon) A. Gray, Amer. Acad. Arts and Sci. Proc. 



19: 78. 1883. 



Spermacoce subulata Pavon ex DC, Prodr. 4: 543. 1830. 



Chiricahua and Huachuca Mountains (Cochise County) , Santa Rita 

 Mountains (Pima County) , 5,000 to 6,000 feet, in woods or in the open, 

 August and September. Southern New Mexico and Arizona; Mexico. 



7. DIODIA. Buttonweed 



Plant annual; stems erect or diffuse; leaf blades narrowly lanceolate; 

 stipules fringed with long, stiff bristles; flowers small, in axillary 

 glomerules; corolla funnelform-salverform, pink; fruit obovoid-turbi- 

 nate, crowned by the persistent calyx lobes. 



1. Diodia teres Walt., Fl. Carol. 87. 1788. 



Gila, Cochise, Santa Cruz, and Pima Counties, 4,000 to 8,000 feet, 

 dry mesas and slopes, often in sandy soil, August and September. 

 Connecticut to Missouri and Arizona, south to Florida and Panama. 



The common form in Arizona is var. angustata Gray, with erect, 

 simple or sparingly branched stems. The typical form, with spreading 

 or procumbent, freely branched stems, also occurs in therState. 



8. MITRACARPUS 



Plant annual; stems erect, simple or sparingly branched; leaves 

 opposite, the blades lanceolate; stipules setose; flowers small, in few, 

 very dense, terminal and axillary clusters; calyx with the 2 pairs of 

 lobes very unlike in size and texture, the larger ones equaling or sur- 

 passing the whitish corolla; capsule didymous, 2-celled 



