i 9 8 BUCKTHORN FAMILY 



Key to the Species 



1. Flower parts in 4's, petals present, large shrub 



or tree 



2. Flower parts in 5's, petals lacking, low shrub 



R. cathartica 

 R. alnifolia 



Rhamnus cathartica L i n n e 1753 Buckthorn 



A shrub or small tree 2-6 m. high; bark brown, twigs often ending 

 in stout thorns; leaves alternate or sometimes opposite, ovate or elliptic, 

 rounded or narrowed at the base, obtuse or acuminate at the apex, mi- 

 nutely serrate, glabrous, 3-6 cm. long, 1.5-3 cm. wide, petioles 1-2 cm. 

 long ; flowers clustered in the axils of the leaves, dioecious, greenish, about 

 4 mm. broad, sepals 4, spreading or reflex, lanceolate, 2 mm. long, petals 

 4, minute, erect, about the same length as the stamens, pedicels 5-8 mm. 

 long, slender; fruit a globose drupe about 8 mm. in diameter, with '3-4 

 grooved nutlets : cathartica, purgative. 



~Rhamr?us cathartica 



rnnus aimioiia 



Frequently planted for hedges. Introduced from Europe and native 

 of that continent and Asia. Flowers in May and June, fruits ripe in 

 August and September. The leaves remain green and are retained on 

 the shrubs until very late in the autumn. 



