776 



TKEES OF NOKTII AMERICA 



IC^ (o^O 



branches forming a round-topped head, and comparatively slender ashy gray 

 branchlets tomentose when they first appear, coated with soft fine pubescence for 

 one or two years and ultimately glabrous. 



Distribution. Mesas and low plains ; desert regions of southern Utah, northern 

 Arizona, southern Nevada, and southeastern California. 



16. Fraxinus Oregona, Nutt. 



Leaves 5'-14' long, with stout grooved and angled pubescent or glabrous petioles, 

 and 5-7 oblong or oval leaflets usually contracted at the apex into short broad points, 

 gradually narrowed at the base, and entire or remotely and obscurely serrate ; when 

 they unfold usually coated below and on the petioles with thick pale tomentum and 

 pubescent above, or nearly glabrous or pilose, with a few scattered hairs, and at 

 maturity thick and firm in texture, light green above, paler and usually tomentose 

 or puberiilous below, 3'-7' long and V-iy wide, with broad pale midribs, conspicu- 

 ous veins arcuate near the margins, and reticulate veinlets, the terminal leaflet raised 

 on a slender petiolule often V in length, the lateral sessile or nearly so, turning yel- 

 low or russet brown in the autumn before falling. Flowers dioecious, appearing in 

 April or May when the leaves begin to unfold, in compact glabrous panicles covered 

 in the bud by broadly ovate scales coated with rufous pubescence ; staminate flower 

 composed of a minute calyx, short filaments, and short-oblong apiculate anthers; 

 calyx of the pistillate flower laciniately cut and shorter than the ovary narrowed 

 into a stout style divided into 2 long conspicuous stigmatic lobes. Fruit in ample 

 crowded clusters, obovate, surrounded at the base by the persistent calyx, 1^-2' 

 long, the body clavate and slightly compressed, with margined edges gradually 

 widening upward into the long many-nerved wing narrowed, rounded, apiculate, or 

 sometimes emarginate at the apex, and about \' wide. 



A tree, frequently 70-80 high, with a long trunk occasionally 4 in diameter, 

 stout branches forming a narrow upright head or a broad shapely crown, and thick 

 terete branchlets at first glabrous or more or less thickly coated with pale or rarely 

 rufous silky tomentum persistent during their second year or occasionally deciduous 

 during their first summer, becoming light red-brown or orange color, glabrous or 

 puberulous, often covered with a slight glaucous bloom, marked by small remote 

 pale lenticels, and during their first and second winters by the large elevated semi- 



