FLOWERING PLANTS AND FERNS OF ARIZONA 579 



1. Hibiscus denudatus Benth., But. Voy. Sulph. 7. 1S44. 



Pinal. Maricopa. Cochise, Pima, and Yuma Counties. March to 

 October. Western Texas to southern California and northern 

 Mexico. 



Two rather well-marked forms occur in Arizona: (1) The typical 

 form of the specie-, a shrub reaching a height of 1 m., with the in- 

 volucel commonly little-developed, growing in sandy washes. 1,500 

 feet or lower, in Pinal. Maricopa, and Yuma Counties; (2) var. 

 iTwoluceUatus Gray II. involucellaius Woot. and Standi.), an under- 

 shrub, commonly not more than 0.5 m. high, with a better developed 

 and more persistent involucel. the prevailing form on shallow "caliche" 

 soils in Cochise and Pima Counties. 2.000 to 4.000 feet. 



2. Hibiscus coulteri Harv. ex A. Gray. PL Wright. 1: 23. 1852. 

 Pinal, Maricopa, Pima, and Yuma Counties, 1.500 to 3.500 feet, 



rather common on rocky slopes and sides of canyons, flowering through- 

 out the year. Western Texas to southern Arizona and Mexico. 

 A straggling shrub, the stems up to 1.2 m. long. 



3. Hibiscus biseptus S. Wats., Amer. Acad. Arts and Sci. Proc. 21: 



418. 1886. 

 Pinal, Maricopa, and Pima Counties. 3.000 to 4.500 feet, not in- 

 frequent on rocky slopes of canyons, April to October. Southern 

 Arizona and northern Mexico. 



Arizona specimens differ from the typical form of the species in 

 having the fine pubescence in only 1 line and the longer hairs mostly 

 forked. 



11. GOSSYPIUM. Cotton 



Plant shrubby; branchlets and petioles quadrangular: leaf blades 

 pedately 3- to 5-parted, with lanceolate or lance-elliptic, attenuate- 

 acuminate lobes; extrafloral nectaries present on the leaf blades and 

 at apex of the peduncles: flowers mostly solitary and axillary, borne 

 on short branches; involucel present, persistent: petals white or whit- 

 ish. 2 to 3 cm. long; fruit a 3- or 4-ceUed loculicidal capsule; seeds 

 turbinate-angulate. rather sparsely villous. 



1. Gossypium thurberi Todaro, Prodr. Monog. Gen. Gossyp. 7. 1878. 



Thwrberia thespesioides A. Gray, Amer. Acad. Arts and Sci. 



Mem. ser. 2. 5: 308. 1855. " 

 Ingenhouzia triloba of authors. Not DC. 



Gila, Pinal. Maricopa. Cochise, and Pima Counties, reported also 

 as occurring in the Bradshaw Mountains (Yavapai County . 2.500 

 to 4.500 (rarely 7.000) feet, rather common on rocky slopes and sides 

 of canyons, late summer and autumn. Southern Arizona and north- 

 ern Mexico. 



A handsome shrub, known in Sonora as " algodoncillo" (little cotton . 

 reaching a height of 4.2 m. (14 feet). Petals normally spotless, but 

 plants with faint crimson basal spots are not rare. The plant i- 

 interesting because a subspecies of the cotton boll weevil breeds in 

 the capsules. The form of this insect of which G. tliurbui is the 

 normal host also occasionally attacks nearby cultivated cotton, conse- 

 quently the United States Department of Agriculture is endeavoring 

 to eradicate the plant where it grows near areas of cotton cultivation. 



