516 CONTRIBUTIONS FKOM THE NATIONAL HEKBAKIUM. 



1. CRESSA L. 



Low herbaceous perennial with slender ascending stems and very numerous small 

 lanceolate entire sericeous leaves; flowers small, axillary, solitary, white; calyx oi 5 

 nearly equal distinct lobes; corolla persistent, the limb 5-lobed; stamens exserted; 

 capsule little longer than broad, the seeds smooth and shining, often solitary. 



1. Cressa truxillensis H. B. K. Nov. Gen. & Sp. 3: 119. 1818. 



Cressa cretica truxillensis Choisy in DC. Prodr. 9: 440. 1845. 



Type locality: "In arenosis salsis Oceani Pacifici, prope Truxillo Peruvianorum." 



Range: California and Utah to Texas and Mexico. 



New Mexico: Mesilla Valley. In heavy soil of river valleys, in the Lower Sono- 



ran Zone. 



2. EVOLVULTJS L. 



Small prostrate or diffuse perennials with more or less densely pubescent stems 

 and small simple entire leaves; flowers solitary in the axils; sepals nearly equal; 

 corolla funnelform or nearly rotate, white or blue, the limb entire; ovary 2-celled, 

 the capsules subglobose, 2 to 4-valved, the seeds 1 to 4. 



KEY TO THE SPECIES. 



Flowers white; upper surface of leaves glabrous 1. E. wilcoxianus. 



Flowers blue; leaves pubescent on both surfaces. 



Pedicels 3 mm. long or less; flowers 10 to 12 mm. in diameter.. 2. E. pilosus. 



Pedicels 25 to 40 mm. long; flowers not more than 8 mm. in 



diameter 3. E. linifolius. 



Evolvulus arizonicus should be found in New Mexico about the southwestern corner. 

 It is similar to E. linifolius but has flowers about 15 mm. broad. 



1. Evolvulus wilcoxianus House, Bull. Torrey Club 33: 315. 1906. 

 Type locality: Near Fort Huachuca, Arizona. 



Range: New Mexico and Arizona and adjacent Mexico. 



New Mexico: Las Vegas; Mangas Springs; Kingston; Water Canyon; San Luis 

 Pass; Organ Mountains. Dry hills and plains, in the Upper Sonoran Zone. 



2. Evolvulus pilosus Nutt. Gen. PI. 1: 174. 1818. 



Evolvulus argenteus Pursh, Fl. Amer. Sept. 187. 1814, not R. Br. 1810. 



Evolvulus nutallianus Roem. & Schult. Syst. Veg. 6: 198. 1820. 



Evolvulus oreophilus Greene, Leaflets 1: 151. 1905. 



Type locality: "On the banks of the Missouri." 



Range: South Dakota and Colorado to Arizona and Mexico. 



New Mexico: Farmington; Raton; Nara Visa; Perico Creek; Albuquerque; Por- 

 tales; Torrance; Socorro Mountain; Hillsboro; Organ Mountains; Leachs Ranch; 

 Redlands. Plains and low hills, in the Upper Sonoran Zone. 



The type of E. oreophilus was collected near Hillsboro (Metcalfe 1228). 



3. Evolvulus linifolius L. Sp. PI. ed. 2. 392. 1762. 

 Type locality: Jamaica. 



Range: Southern New Mexico and Arizona to Mexico and the West Indies. 



New Mexico: Carrizalillo Mountains; Organ Mountains. 



Our specimens are scarcely typical, having more abundant pubescence and larger 

 flowers than the southern forms. They probably belong to an undescribed species, 

 but it seems inadvisable to attempt to separate them until the difficult genus can be 

 carefully revised. 



