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



and Pima Counties), 2,500 to 4,500 feet, dry slopes and mesas, 

 common and in many places abundant, May to August. Arizona and 

 northern Sonora. 



Sometimes known locally as "paloverde," a name properly belong- 

 ing to Parkinsonia and Cercidium. This striking and peculiar plant 

 is a characteristic feature of the landscape in large areas of southern 

 and western Arizona. The trees attain a height of at least 4.5 m. 

 (15 feet). The living branches burn readily, as if resinous (pi. 17). 



69. ACER ACE AE. Maple family 

 1. ACER. Maple 



Trees or large shrubs; leaves opposite, simple or palmately or 

 pinnately compound; flowers small, perfect or unisexual, in cymose 

 or racemose, mostly axillary inflorescences; petals present or absent; 

 stamens 4 to 12, borne on a ring-shaped disk, or the disk sometimes 

 obsolete; fruit a pair of laterally winged samaras, these united at base. 



All of the maples are ornamental, but the genus is of minor import- 

 ance in Arizona. In autumn the leaves change color and give great 

 beauty to the mountain scenery. It is reported that maple sugar is 

 sometimes made from the sap of A. grandidentatum. The plants are 

 browsed by livestock and deer. 



Key to the species 



1. Leaves pinnately compound, 3- to 5-foliolate, the terminal leaflet long- 

 stalked 1. A. NEGUNDO. 



1. Leaves simple or palmately trifoliolate, the terminal leaflet sessile or short- 

 stalked (2). 

 2. Leaf blades thin, glabrous, with numerous acute teeth; inflorescence long- 

 stalked 2. A. GLABRUM. 



2. Leaf blades thickish, usually persistently pubescent beneath, with few obtuse 

 teeth; inflorescence nearly sessile 3. A. grandidentatum. 



1. Acer negundo L., Sp. PI. 1056. 1753. 



Apache County to Mohave County, south to Cochise and Pima 

 Counties, 5,000 to 8,000 feet, common along streams, April. Through- 

 out most of the United States. 



Boxelder. A rapid-growing tree, reaching a height of 15 m. (50 

 feet) and a trunk diameter of 0.8 m. (2.5 feet). It is often planted in 

 dooryards and along streets, but is short lived and subject to damage 

 by windstorms. The trunk is short, the crown broad, rounded, and 

 dense, the bark pale grayish brown, and the wood soft and light- 

 colored. The species is represented in Arizona by var. interius 

 (Britton) Sarg., which differs from the typical eastern form of A. 

 negundo in its somewhat thicker, commonly more pubescent leaves. 

 There is intergradation, however, and the form described as var. 

 arizonicum Sarg. (type from the Santa Catalina Mountains, Rehder 

 463) approaches the eastern form in its thin, very sparingly pubescent 

 leaves. 



2. Acer glabrum Torr., Ann. Lye. N. Y. 2: 172. 1828. 



Coconino County to Cochise County, 7,200 to 9,000 feet, rich soil of 

 coniferous forests, May to June. South Dakota to Alaska, south to 

 New Mexico, Arizona, and California. 



