FLOWERING PLANTS AND FERNS OF ARIZONA 223 



25. FAGACEAE. Beech family 



1. QUERCUS. Oak 

 Contributed by C. H. Muller 



Trees or shrubs ; leaves alternate, simple, petioled, the blades entire, 

 toothed, or lobed, persistent or deciduous; stipules associated with 

 the buds, ligulate, often caducous; flowers monoecious; staminate 

 flowers in flaccid pendulous aments, the perianth about 5-lobed, the 

 stamens 5 to 10, free; pistillate flowers solitary or clustered, subsessile 

 or peduncled, enclosed in an involucre of numerous flat scales, the 

 perianth 6-lobed, the ovary 3-carpellate, 1-celled, the ovules 6 (5 

 abortive), the styles 3, short; fruit a nut (acorn), 1-seeded, partly 

 enveloped by an involucre (cup) of flat or basally thickened scales, 

 maturing in 1 or 2 seasons. 



The shrubby or scrub oaks, such as Q. turbinella, are the principal 

 elements of the chaparral on exposed mountainsides in southern and 

 central Arizona. In this region they are considered the chief reserve 

 winter feed for cattle, and in addition are of inestimable value in 

 retarding soil erosion. Some of the tree oaks of southern Arizona 

 (Q. arizonica, Q. emoryi, etc.) are also important browse plants. At 

 higher elevations, especially in northern Arizona, the deciduous white 

 oaks, principally Q. gambelii, are abundant and provide ground cover 

 as well as browse for livestock and deer. Although livestock may 

 suffer poisoning when feeding exclusively on oak browse, the foliage 

 is fairly nutritious if supplemented with other feed. The fattening 

 effect of acorns, especially for swine, is well known. They are an 

 important food of birds, squirrels, and other wild animals. The 

 Indians gathered acorns for food, generally roasting them and often 

 making a meal which they mixed with meat or fat. Although the 

 Arizona oaks afford valuable shade on cattle ranges, they rarely 

 attain sufficient size for logging. The wood is used locally for fuel, 

 fence posts, and mine props. Oak bark is one of the principal sources 

 of tanning material. 



Key to the species 



1. Shell of the fruit tomentose within; abortive ovules lateral or apical; cup scales 

 thin and flat or, if thickened, then covered with a dense golden tomentum; 

 stigmas short and broad or elongate, spatulate (2). 

 2. Cup scales basally thickened, covered with a dense golden tomentum, the 

 cup large, heavy, loosely fitting the acorn; stigmas short and broad; 

 abortive ovules lateral; leaves glaucous, dull, usually yellow and resin- 

 ous-pubescent beneath, the blades ovate, the lobes mucronate to long- 

 aristate, the margin markedly crisped, concave beneath: Subgenus 



Protobalanus, Intermediate oaks 11. Q. palmeri. 



2. Cup scales thin, flat, thinly scurfy-pubescent with gray or buff hairs, or 

 glabrate, the cup medium-sized, closely fitting the acorn; stigmas elon- 

 gate, spatulate; abortive ovules apical; leaves not glaucous or resinous, 

 the blades lanceolate, usually not long-aristate, the margins flat or revo- 

 lute, not crisped or concave: Subgenus Erythrobalanus, Black oaks (3). 

 3. Leaves flat, broadly lanceolate, usually distinctly cordate at base and 

 subentire, or with a few short apical teeth, green on both sides, with 

 a small tuft of stellate tomentum at base of the midrib beneath, other- 

 wise glabrate 12. Q. EMORYI. 



3. Leaves revolute, usually narrowly lanceolate or attenuate, cuneate or 

 rarely rounded at base, entire or with several short teeth or small 

 lobes above the middle, glaucous green and glabrate or nearly so above, 

 densely white-tomentose beneath 13. Q. HYPOLEroomEs. 



l>n<;744°— 42 15 



