RHAMNACEAE 



Cascara Buckthorn 

 Rhamnus purshiana DC. 



HABIT. A shrub or tree 20-40 feet high and 6-20 inches in 

 diameter; wide, open crown with numerous, stout branches. 



LEAVES. Ahernate, or rarely obUquely opposite; simple; 

 broad-elliptic; 2-7 inches long; undulate margins finely serrate 

 or nearly entire ; thin ; villous below and on veins above ; decidu- 

 ous; turning pale yellow before falling; petioles stout, hairy, 

 V^-l inch long; stipules minute, deciduous. 



FLOWERS. Regular; perfect; small; in axillary peduncled 

 cymes; long-pedicelled ; calyx 5-lobed; corolla greenish, ninute, 

 5-lobed; stamens 5; ovary 2-4-celled; ovules solitary, erect. 



FRUIT. Drupaceous; subglobose; V?,-V2 inch in diameter; 

 black; bearing remnants of style; flesh thin and juicy; with 2-3 

 obovoid, 1 -seeded nutlets with a thin, gray or yellow-green shell. 



TWIGS. Slender; round; pubescent, usually becoming gla- 

 brous; yellow-green or red-brown. Winter buds: terminal absent; 

 lateral small, naked, hoary-tomentose. 



BARK. Thin (K inch); gray to dark brown, often tinged 

 with red; scaly; important because of laxative properties. 



WOOD. Unimportant; rather light; soft; not strong; ring- 

 porous; heartwood brown, tinged with red. 



SILVICAL CHARACTERS. Moderately tolerant; prolific 

 seeder and coppices freely; no taproot; few enemies. 



GENERAL. A related shrubby form, R. purshiana var. bet- 

 ulaefolia (Green) Cory, is shown in the Southwest on the 

 map. Three native and two naturalized species reach tree size 

 and are keyed out below. 



1. Winter buds scaly; leaves oval to broad-ovate. 



2. Leaves deciduous, thin, opposite or nearly so, finely crenate- 



serrate ; fruit black ; naturalized 



R. cathartica L., European Buckthorn 



2. Leaves persistent, thick, mostly alternate, spiny-toothed; fruit 

 red; California and Arizona 



. . .R. crocea var. ilicifolia Greene, Hollyleaf Buckthorn, p. 317. 

 1. Winter buds naked; leaves entire or finely toothed. 



3. Leaves deciduous, thin. 



4. Flowers in umbel-like cymes; leaves 2-7 inches long, with 8-15 

 pairs of veins; native. 



5. Leaves with 10-15 pairs of veins; peduncles longer than 



petioles; West Coast R. purshiana DC, Cascara Buckthorn 



5. Leaves with 8-10 pairs of veins; peduncles shorter than 



petioles; Southeast 



R. caroliniana Walt.. Carolina Buckthorn 



4. Flowers fascicled or solitary; leaves 1 M-2 >2 inches long, with 



8-9 pairs of veins ; naturalized 



R. frangula L., Glossy Buckthorn 



3. Leaves persistent thick; southeastern California to Nevada and 



New Mexico R. calif ornica var. ursina (Greene) McMinn, 



California Buckthorn 



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