36 RHAMNACE2E. (BUCKTHORN FAMILY.) 



tical, 1 to 4 inches long, denticulate or nearly entire; petals very small, broadly ovate, 

 emarginate; fruit blackish-purple. 



2. CEANOTHUS, L. 



Calyx 5-cleft; the lobes acute; disk thick adhering to the tube and to the ovary; petals 

 on long claws, hooded; stamens 5; filaments long-exserted; ovary 3-lobed; style short, 

 3-cleft. The small flowers are in showy thyrsoid or cymose clusters. Species difficult. 



1. Leaves 3-nerved. 



1. C. thyrsiflorus, Esch. (CALIFORNIA LILAC. ) Smooth, 6 to 15 ft. high; branches 

 strongly angled; leaves rather thick, oblong to oblong-ovate, 1 to 1 inches long, usually 

 smooth and shining above, canescent beneath; flowers bright blue in dense compound 

 racemes, terminating the long and somewhat leafy peduncles. 



2. C. integerrimus, Hook & Arn. Slender, 2 or 3 ft. high; branches round, usually 

 warty; leaves thin, bright green, ovate to ovate-oblong, 1 to 3 inches long; thyrse large, 

 white-flowered. 



3. C. dentatus, Torr & Gr. Low, not rigid; leaves small glandular-serrate, 

 fascicled, the margin strongly undulate or revolute, somewhat resinous; flowers blue, in 

 small roundish clusters. 



4. C. sorediatus, Hook & Aru. Kigid; inflorescence pubescent; leaves silky on 

 the nerves, ^ to 1^ inches long; flowers blue in shortly peduncled simple racemes to 2 

 inches long. 



5. C. divaricatus, Nutt. Grayish, usually spinose; leaves small, not tomentose 

 beneath; flowers light blue or white, in nearly simple often elongated racemes, 1 to 4 

 inches long; fruit resinous. 



C. C. incanus, Torr & Gr. Spinose; leaves hoary beneath with a very minute 

 tomentum, cuneate to cordate at base; flowers in short racemes, white; fruit resinously 

 warty. A straggling shrub along creeks. 



2. Leaves pinnately veined. 



7. C. papillosus, Torr. & Gr. More or less hispidly villous or tomentose, 4 to 6 

 ft. high; leaves glandular-serrulate, and the upper surface glandular-papillose, narrowly 

 oblong, 1 to 2 inches long on slender petioles; flowers blue, in close clusters or short 

 racemes, terminating slender naked peduncles; fruit not resinous. 



3. Leaves small, often opposite, very thick, with numerous straight lateral veins; stipule* 

 mostly large and warty; Jlowers in sessile or shortly peduncled axillary clusters; fruit 

 larger, toith 3 horn-like or warty prominences below the summit. 



8. C. crassifolius, Torr. Erect 4 to 12 ft. high, the young branches white with a 

 villous tomentum; leaves somewhat spinosely-toothed or rarely entire and revolutely 

 margined; flowers ligH, blue or white, in dense clusters. 



