THE BUCKTHORN FAMILY 



RHAMNACEiE Dumortier 



HIS family consists of about 46 genera including nearly 600 species of 

 trees, shrubs or vines, with or without spines. They are of wide dis- 

 tribution in both temperate and tropical regions and are of considerable 

 economic importance on account of the bitter and astringent principle 

 contained in many, rendering them of much value in medicine and in the art of 

 tanning. One of the most important and most generally used American drugs, 

 Cascara Sagrada, is the bark of Rhamnus Purshiana de CandoUe a small tree of 

 the northwestern United States and adjacent British Columbia. Rhamnus cathartica 

 Linnseus, of which the fruit under the name Buckthorn berries is used, and Rham- 

 nus Frangula Linnaeus, of which the bark is used, are two well-known European 

 drugs; the fruits of various species of Zizyphus, known as Jujube berries, are edible. 

 The RhamnacecB have alternate, rarely opposite, prominently nerved, simple 

 leaves, with small stipules which in some species fall away early. The flowers are 

 small, regular, perfect or polygamous, sometimes dioecious, and variously clustered. 

 The calyx is 4-lobed or 5-lobed, the lobes valvate; disk fleshy, lining or filling 

 the calyx- tube; the corolla, when present, consists of 4 or 5 petals, inserted on the 

 calyx and alternate with its lobes; stamens 4 or 5, inserted with and opposite the 

 petals; filaments distinct; anthers versatile, 2-celled; ovary partly immersed in 

 the disk, 2-celled or 3-celled; styles and stigmas more or less united; ovules soKtary 

 or rarely 2 in each cavity and erect. The fruit is capsular or drupe-Uke, rarely 

 winged; seeds solitary in each cell, smooth or furrowed, their endosperm fleshy 

 or sometimes none; cotyledons usually very broad. 



There aje a number of genera, represented by shrubs or climbers, in addition 

 to the following ones, containing arborescent species, occurring in our area : 



Fruit more or less fleshy. 

 Fruit pulpy, with a 3-celled stone. ' 

 Petals absent. 

 Sepals crested; leaves usually opposite. 1. Krugiodendron. 



Sepals not crested. 

 Leaves opposite, evergreen; branches not spiny. 2. Reynosia. 



Leaves alternate, deciduous; branches spiny. 3. Condalia. 



Petals present. 4. Karwinskia. 



Fruit dryish, with 2 or 3 nutlets. 5. Rhamnus. 



Fruit dry and hard, separating into 3 parts. 

 Sepals inflated; petals with slender claws. 6. Ceanothus. 



Sepals spreading; petals without claws. 7. Colubrina. 



671 



