BUCKTHORN BERRIES 425 



reddish-brown, having numerous grayish lichens and obscure light- 

 brown lenticels from 1 to 2 mm. in width; inner surface grayish or 

 dark brown and longitudinally striate; fracture short-fibrous; odor 

 slight; taste bitter and astringent. The older pieces are distin- 

 guished by having a deeply fissured cork and groups of stone cells. 

 In the younger bark the medullary rays are from 4 to 7 cells in width. 



RHAMNUS CATHARTICUS. Fructus Rhamni Catharticae, Buck- 

 thorn Berries. The ripe fruit of Rhamnus catharticus (Fam. 

 Rhamnacese), a thorny shrub, indigenous to northern Africa 

 and central Asia, widely distributed in Europe, and naturalized 

 locally in the eastern United States. The fruits are collected when 

 they are ripe, in September and October, and used either in the fresh 

 or dried condition. Most of the supply of the drug is obtained from 

 Hungary. 



Description. When fresh, nearly globular or ovoid, from 4 to 8 

 mm. in diameter; externally greenish-brown or purplish-black, 

 having at the upper portion a ring-like disc with 4 calyx teeth, and 

 at the lower portion a short stalk, which is usually lacking in the dried 

 fruit ; epicarp dark violet ; sarcocarp greenish ; endocarp light yellow, 

 papery; 4-locular, containing a single seed in 2 or 3 of the locules; 

 seeds anatropous, triangular-convex; the raphe extending in a deep 

 ridge; externally dark reddish-brown and internally light brown; 

 odor slight and unpleasant; taste sweetish, bitter and acrid. The 

 pericarp colors the saliva yellowish. 



Inner Structure. (Fig. 186.) An epidermal layer of dark violet, 

 thick-walled cells; a hypodermis of 5 rows of collenchymatous 

 cells, some of which contain rosette aggregates of calcium oxalate; 

 sarcocarp composed mostly of thin-walled radially elongated cells, 

 among which are the large secretion cells having a yellowish, highly 

 refracting, oily content; an endocarp of several layers, the outer 

 consisting of stone cells having small prisms of calcium oxalate, a 

 layer beneath of tabular cells, a third layer the cells having crystals 

 of calcium oxalate, and an inner layer of sclerenchymatous fibers; 

 inner epidermis of pericarp of large thin-walled cells, containing a 

 yellowish amorphous substance; seed-coat having an epidermal layer 

 made up of thick-walled porous cells, beneath which are several layers 

 or more or less collapsed cells; cells of endosperm and embryo con- 

 tain an oily cytoplasm and numerous aleurone grains. Sections of 

 the pericarp of the fresh fruit are colored purplish-red upon the addi- 

 tion of acids and bright green on addition of solutions of the alkalies. 



Constituents. Rhamnoemodin, being apparently the most active 

 principle (see Rhubarb). A mixture of 3 distinct coloring principles 



