FOREST TREES OF THE PACIFIC SLOPE. 401 



twigs or seemingly in pairs, the two leaves nearly but rarely exactly opposite 

 each other. Minute flowers, bisexual, or some of them male and others female, 

 and each kind borne on different trees, occur in small branched or unbranched 

 clusters at the bases of leaf-stems, coming after the latter are grown. Fruits 

 matured in one season (usually in late summer) resemble berries and have a 

 thick, juicy pulp covering from 2 to 4 very hard seeds, somewhat like a coffee 

 grain. The succulent, often attractive fruits are greedily eaten by birds and 

 mammals (without injury to the seeds). They are widely disseminated, chiefly 

 in this way. Wood of the buckthorns is fine to coarse grained, moderately 

 heavy and firm, of ordinary quality, and of no economic value, principally 

 because the trees are small. The best known species of the group is the Euro- 

 pean Buckthorn (Rhamnus cathartica I,. I, popular for hedges and as a small 

 ornamental tree. Several of our native species are planted for ornament, but 

 one only, a tree of the Pacific region, is of commercial importance on account of 

 its medicinal bark. Three tree species and one variety occur in the United 

 States, and two of these inhabit the Pacific region. 



Evergreen Buckthorn. 

 Rhamnus crocea Nuttall. 



DISTINGUISHING CHARACTERISE! S. 



Evergreen buckthorn has glossy, prickly, evergreen leaves, and is very com- 

 monly only a straggling or massed shrub from 2 to 4 feet high, but in protected 

 situations it is sometimes a slim tree from 12 to 15 feet high, with a smoothish, 

 dull ashy gray trunk from 3 to G inches through ; crown branches few and 

 distant. The smooth, red-brown twigs are straight, stiff, some of them spine- 

 like. Mature leaves smooth throughout (fig. 190), thinnish but leathery, shiny 

 yellowish green on their top sides, and much lighter, sometimes reddish green 

 beneath ; occasionally very minutely hairy on the veins and leaf stems. Fruit 

 (fig. 190), ripe in late summer, dull red. and smooth; the very thin pulp covers 

 from 1 to 3 little nuts, which split open and liberate a hard, grooved seed pointed 

 at one end (fig. 191, a ) . Wood, light yellowish-brown, line-grained, and brittle. 

 Of no economic use. 



Longevity. — Not fully determined. One tree 3g inches in diameter showed 

 an age of 29 years. 



A distinct variety of this species which possibly deserves to rank as a species 

 is Rhamnus crocea insularis (Greene) Sargent, which occurs on Cedros and 

 Santa Barbara islands and the adjacent mainland of California. It differs from 

 the species in its longer and less distinctly toothed leaves (fig. 191), sometimes 

 with entire borders; in its somewhat larger flowers and bright red fruit; and 

 particularly in the uniformly grooved, rounded, and abruptly short-pointed top 

 end of the seed. Said to be 25 or 30 feet high and to flower six weeks later 

 than Rhanuuis crocea. Specimens of this variety have not been compared with 

 those upon which Rhanuuis piriform Greene, found on Santa Cruz Island, is 

 based. The latter appears to be a form of this variety. 



What is probably another, but less well known, variety is Rhamnus crocea 

 pilosa Curran, found in Santa Maria Valley near San Diego, Cal. It h;is nar- 

 rower leaves with curled borders, and the twigs and leaves are covered with 

 dense, minute, soft hairs. Nothing is known of its size. 



California; upper Sacramento River, west of Sierra Nevada Mountains (to latitude 29 ) 

 to Lower California (Guadalupe Islands). 



