70 RHAMNACE^E. 



ORDER XXXV. RHAMNACE^. BUCKTHORNS. 



Calyx 4 5 -cleft, valvate. Petals distinct, inserted into the 

 orifice of the calyx, occasionally wanting. Stamens definite, 

 opposite the petals. Disk fleshy. Ovary superior or half su- 

 perior, 2 3 4-celled. Fruit fleshy and indehiscent, or dry 

 and separating in 3 parts. Seeds erect, mostly with fleshy al- 

 bumen ; embryo with large flat cotyledons. Trees or shrubs, 

 often thorny. Leaves mostly alternate, simple, usually with 

 minute stipules. 



1. RHAMNUS. Linn. Buckthorn. 



(From the Greek pa/*i/pj, while-thorn ; probably from its resemblance to some 

 of the thorn tribe.) 



Calyx 4 5-cleft, urceolate. Petals alternating with the 

 lobes of the calyx, sometimes very minute or wanting. Sta- 

 mens 4 5, inserted above the petals. Style 2 4-cleft. Fruit 

 drupaceous, roundish, containing 2 4 cartilaginous nuts. 



1. R. alnifolius L'Herit: unarmed; leaves alternate, oval, acuminate, 

 serrulate, pubescent on the veins beneath ; flowers dioecious ; peduncles 

 1-flowered, aggregate ; calyx acute ; fruit turbinate. R. franguloides 

 Mich. 



Sphagnous swamps. Hudson's Bay to Penn. ; rare. May, June. fy. Stem 

 2 4 feet high, branching. Flowers small, greenish, in axillary fascicles. Berries 

 black, the size of a small pea. R. alnifolius of Pursh is described by De Can- 

 dolle as a distinct species, under the name of R. Purshianus. 



Alder-leaved Buckthorn. 



2. R. catharticus Linn. : branches thorny at the top ; leaves opposite, 

 ovate, erosely denticulate ; flowers mostly 4-cleft, polygamo-dioecious ; ber- 

 ries 4-seeded, subglobose. 



Highlands of N.Y. Torr. Mass. A small tree or large shrub, with yellowish- 

 green flowers. Fruit black ; cathartic. Introduced ? Common Buckthorn. 



2. CEANOTHUS. Linn. Ceanothus. 

 (An ancient Greek name applied to this genus.) 



Calyx 5-cleft, campanulate, persistent and somewhat ad- 

 hering with the fruit. Petals 5, small, saccate and arched, 

 with long claws. Stamens exsert. Styles 2 3, united to the 

 middle. Fruit dry and coriaceous, 3-celled, 3-seeded, 3-parted, 

 opening on the inner side. 



1. C. Americanus Linn. : stem shrubby ; branches terete, and somewhat 

 pubescent; leaves ovate-oblong, alternate, serrate, 3-nerved, tomentose, 

 pubescent beneath ; common peduncles axillary, elongated, almost leafless. 

 C. kerbaceus Raf. 



