388 MISC. PUBLICATION 42 3, XT. S. DEPT. OF AGRICULTURE 



1. Crossosoma bigelovii S. Wats., Amer. Acad. Arts and Sci. Proc. 



11: 122. 1876. 



Southern parts of Yavapai, Mohave, and Gila Counties to Pinal, 

 Maricopa, Pima, and Yuma Counties, 4,000 feet or (usually) lower, 

 dry rocky slopes and cliffs, February to May (rarely September). 

 Southern and western Arizona, southeastern California, and north- 

 western Mexico. 



A straggling shrub, up to 2.4 m. (8 feet) high, with very astringent 

 bark and white flowers, these sometimes tinged with purple. Worthy 

 of cultivation on account of the delicious fragrance of the flowers. 

 In the eastern part of its range, var. glaucum (Small) Kearney and 

 Peebles (C. glaucum Small) largely replaces the typical form. The 

 variety is distinguished by broader and more glaucous follicles, but 

 intergradation between the two forms is complete. The type of 

 C. glaucum is Palmer 560, Arizona, without definite locality. 



2. Crossosoma parviflorum Kobins. and Fern., Amer. Acad. Arts and 



Sci. Proc 30: 114. 1894. 

 Known certainly only from the type specimen collected in the 

 Grand Canyon (Gray in 1885), with fruit only. The material is 

 insufficient to permit a conclusion as to whether this form is specifically 

 distinct from C. bigelovii. 



53. ROSACEAE. Rose family 



Plants herbaceous or woody; leaves alternate (except in Coleogyne), 

 simple or compound, usually with stipules; flowers mostly perfect, 

 regular or nearly so; sepals partly united; petals commonly 5, occa- 

 sionally none; stamens commonly numerous, rarely fewer than 5, 

 nearly always borne on the throat of the calyx or on a disk surround- 

 ing the ovary or ovaries; pistils 1 to many; ovary free from or adnate 

 to the calyx; fruit various. 



This large and very diverse family includes many of the most 

 important cultivated fruits, such as the apple, pear, peach, plum, 

 cherry, apricot, almond, strawberry, raspberry, and blackberry. 

 The flowers and foliage are usually attractive, often beautiful, and 

 many plants of this family, first and foremost the roses, are highly 

 prized as cultivated ornamentals. Many of the species in Arizona 

 are important browse plants, both for domestic animals and deer, 

 and the fruits supply much food for birds and other wild animals. 

 Most of the Rosaceae are harmless, but a few are reputed to be some- 

 what poisonous. 



Key to the genera 



1. Carpel solitary; fruit a dry or fleshy, usually 1-seeded drupe (plumlike); calyx 

 more or less persistent at base of the fruit; plants small trees or large shrubs; 

 leaves simple; flowers white or greenish, in racemes or corymbs, or solitary 



in the leaf axils 22. Prunus. 



1. Carpels more than one or, if solitary, the fruit an achene (2). 



2. Ovary inferior, enclosed in and adnate to the calyx tube (hypanthium) , the 

 latter becoming more or less fleshy; fruit a pome (applelike); calyx 

 lobes more or less persistent at apex of the fruit; plants shrubby or tree- 

 like; petals white (3). 

 3. Leaves pinnate; flowers small, in short broad compound many-flowered 

 cymes 6. Sorbus. 



