46 KHAMNACE^E. (BUCKTHORN FAMILY.) 



ORDER 20. CELASTRACE^E. (STAFF-TREE FAMILY.) 



Shrubs, with simple leaves, no stipules, and small dull-colored perfect 

 regular flowers, the stamens as many as the petals and inserted on the 

 margin of a broad disk which lines the calyx-tube. Sepals and petals 

 imbricated. Stamens alternate with the petals. Seeds arillate. 



1. PACHYSTIMA, Kaf. 



Calyx with a short tube and 4 rounded lobes. Petals 4. Ovary free, 

 2-celled : style very short. Capsule small, coriaceous, 1 to 2-seeded. Seeds 

 enclosed in a white many-cleft membranaceous aril. Low evergreen shrubs ; 

 leaves smooth, opposite, very shortly petioled, serrate or serrulate ; flowers 

 green, in one to few-flowered axillary cymes. 



1. P. Myrsinites, Raf. Leaves ovate to oblong or oblanceolate, cuneate 

 at base: fruit smooth. In the mountains from New Mexico to British 

 America and westward to California. In dense clumps on wooded slopes. 

 The only other species known (P. Canbyi) grows at a single station in the 

 Alleghany Mountains of Virginia. 



ORDER 21. RHARINACE^E. (BUCKTHORN FAMILY.) 



Shrubs or small trees, with simple undivided leaves, small arid often 

 caducous stipules, and small regular flowers. Sepals valvate in the 

 bud ; a conspicuous disk lining the short tube of the calyx. Petals 

 clawed, mostly involute, each around a stamen in the bud, sometimes 

 wanting. Stamens perigynous and alternate with the sepals. In ours 

 the fruit is berry-like or dry, containing 2 to 4 separating seed-like nut- 

 lets, and the leaves are alternate. 



1. Ilhamims. Calyx and disk free from the ovary ; calyx-lobes erect or spreading. 



Petals small, short-clawed, or none. Filaments very short. Fruit berry-like, with 2 

 to 4 mostly indehiscent nutlets. 



2. Ceanothus. Calyx and disk adnate to the base of the ovary ; calyx-lobes connivent. 



Petals long-clawed, hooded. Filaments exserted. Fruit diy, with 3 dehiscent 

 nutlets. 



1. RHAMNUS, L. BUCKTHORN. 



Flowers perfect or polygamo-dioecious. Calyx 4 to 5-cleft. Petals on the 

 margin of the disk. Leaves pinnately veined, with small deciduous, stipules, 

 and greenish flowers axillary cymose or racemose. 



1. Seeds and nutlets deeply siilcute or concave on the back : flowers mostly 



dioecious, solitary or fascicled in the axils. RHAMNUS proper. 

 1. R. alnifolia, L'Her. A shrub 2 to 4 feet high: leaves deciduous, 

 - ovate-oblong, crenately serrate : petals wanting : fruit black, obovate, 3-lobed. 

 W. Wyoming, westward, and eastward across the continent. 



