BUCKTHORN FAMILY. 



255 



are chiefly of the Pacific United States. All of our species are ever- 

 green except 0. integerrimus and C. Parryi. According to the field 

 investigations of Mrs. K. Brandegee, the nearly related species give 

 rise to numerous hybrids. Of. Proc. Cal. Acad , 2d Ser., iv. 173.) 



A. Leaves alternate. 



Fruit smooth or at most crested, never with horns; stipules thin or mem- 

 branous, fugacious or deciduous. 

 Branches flexible, not spinescent. 

 Flowers white; leaves plane. 

 Inflorescence compound; leaves very strongly 3-nerved beneath, V/^ 



to 3 in. long; fruit slightly crested 1. C. vdutinus. 



Inflorescence simple or compound; leaves entire, % to 1 in. long; fruit 



crestless 2. C. inttg^rrnnus. 



Flowers blue (rarely varying to white); inflorescence compound. 

 Leaves plane, mostly L to 1% in. long, strongly 3-nerved, serrulate . . . 



3. C. thyrsiflorus. 



Leaves similar, pinnately veined, but the margins revolute, seemingly 

 entire, and sometimes concealing the supplementary lateral 



nerves 4. C. Parryi. 



Flowers blue, the clusters in a simple raceme mostly.^ to 1 in. long; 

 leaves mostly rather small, usually not 3-nerved. 

 Leaves subcoriaceous, with smooth waxy surface, the margin very 



glandular-serrate 5. C. foliosus. 



Leaves papillate near the revolute margin 6. C. dtntatm 



Leaves similar, but glandular-papillate on the entire upper surface . . 



7. C. papillosus. 



Branches more or less rigid and spinescent. 



Leaves glandular-serrate; flowers deep or very light blue, in a simple 



raceme; branchlets stiff 8. C. sortdiatus. 



Leaves entire; flowers white, in a simple or paniculately compound 

 raceme; branchlets thick and stout, spur-like, very glaucous; fruit 

 warty-roughened; leaves strongly 3-nerved . ... 9. 6*. incanu*. 



B. Leaves opposite. 



iFruit with conspicuous dorsal horns; stipule-bases warty or cork-like and 

 persistent. 

 Ereet shrubs. 



Flowers white; leaves entire 10. C. can cat us. 



Flowers blue; leaves finely spinose-dentate on the upper half 



11. C. rigidus. 



Flowers blue (or white); leaves rather coarsely spinose-dentate. 



Branchlets gray; pedicels 2 lines long 12. C. Jtpsonii. 



Branchlets reddish or brownish; pedicels 5 to 7 lines long 



13 C. purpurea. 



Low-spreading shrub; flowers blue; leaves coarsely few-toothea toward 

 the apex: var. divergens of ". . 14. C. prostratus. 



1. C. velutinus Dougl. Sxow Brush. Large shrub, 8 to 12 ft. 

 high, the branches mostly ascending; odor very sweet and benvy; 

 leaves elliptic or ovatish, rounded or subcordate at base, finely 

 glandular-serrate, pale and strongly 3-nerved beneath, varnished 

 above and frequently of a rich chocolate-brown, 1£ to 3 in. long, on 

 petioles % in. long or less; panicle 2 to 3 in. high; flowers white, 2 

 lines broad; fruit smooth, lobed at top, nearly crestless, sticky- 

 gland ular. 



Mt. Shasta; Modoc Co.; and the northern Sierra Nevada 

 Yar. laevigatus T. & G. Subarborescent; leaves glabrous, light 

 green; inflorescence more ample; fruit somewhat crested. — Mt. St. 

 Helena and northward in the Coast Ranges to Mendocino and Hum- 

 boldt Cos. 



