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



species; calyx 4- or 5-lobed; petals present or absent in the staminate 

 flowers, the stamens several to many; petals absent or rudimentary 

 in the pistillate flowers, the ovary 3- or sometimes 2-celled, the 

 ovules solitary, the styles 3 or sometimes 2, 1-to 4- times bifid; capsules 

 3-or sometimes 1-seeded; seeds small to medium, carunculate. 



These plants are malodorous and probably more or less poisonous. 

 The powerful purgative, oil of croton, is obtained from an Asiatic 

 species, C. tiglum L. 



Key to the species 



1. Shrub; leaves green, glabrate above; flowers monoecious, the staminate 

 flowers with petals 1. C. soxorae. 



1. Suffruticose perennials, or annuals; leaves gray with stellate hairs or, if green 

 and glabrate above, then the flowers dioecious and the staminate flowers 

 without petals (2) . 

 2. Flowers mostly monoecious; staminate flowers petalif erous ; glandular disk 

 of the pistillate flowers 4- or 5-lobed; styles once bifid (3). 

 3. Suffruticose perennial; anthers about 1.5 mm. long_ 2. C. corymbulosus. 

 3. Annual; anthers about 0.5 mm. long (4). 



4. Ovary 3-celled; capsule 3-seeded; styles 3; staminate calyx 5-lobed. 



3. C. LINDHEIMERIANUS. 



4. Ovary 2-celled; capsule 1-seeded; styles 2; staminate calyx 4-lobed. 



4. C. MONANTHOGYNUS. 



2. Flowers dioecious; staminate flowers apetalous; styles 2 or more times 

 bifid; glandular disk entire, or minutely crenulate, or sometimes lobed 

 in C. texensis (5). 

 5. Perennial; upper surface of the leaf densely covered with overlapping 



stellate hairs, hence grayish 5. C. californicus. 



5. Annual ; upper surface of the leaf sparsely clothed with rarely overlapping 

 stellate hairs, hence green 6. C. texensis. 



1. Croton sonorae Torr., U. S. and Mex. Bound. Bot. 194. 1859. 

 Western part of Pinal and Pima Counties, dry rocky slopes. 



Southern Arizona and Mexico. 



2. Croton corymbulosus Engelm. in Wheeler, U. S. Survey West 



100th Merid. Rpt. 5: 242. 1878. 



Croton eremophilus Wool, and Standi., Contrib. U. S. Natl. 

 Herbarium 16: 144. 1913. 



Greenlee, Cochise, Santa Cruz, and Pima Counties, 2,600 to 6,000 

 feet, common on dry rocky slopes, type from Camp Bowie, Cochise 

 County (Rothrock 506). Texas to southern Arizona and northern 

 Mexico. 



The leaves are reported to be used in domestic medicine, in Texas. 



3. Croton lindheimerianus Scheele, Linnaea 25: 580. 1853. 



The solitary specimen seen from Arizona, perhaps introduced, was 

 collected at Beaver Creek, Yavapai County (C. A. Purpus 8258). 

 Kansas to Texas and northern Mexico. 



4. Croton monanthogynus Michx., Fl. Bor. Amer. 2: 215. 1803. 



In Arizona known only from the Santa Cruz River at La Noria, 

 Santa Cruz County (Mearns 1167), perhaps introduced from farther 

 east. Florida to Illinois and Texas. 



5. Croton californicus Muell. Arg. in DC, Prodr. 15 2 : 691. 1866. 

 Rillito Creek (Pima County), Verde River (Maricopa (?) County), 



Parker and Yuma (Yuma County), 200 to 2,300 feet. Southwestern 

 Arizona, California, and Baja California. 



