GUARANA 415 



Description. Cylindrical sticks, 15 to 30 cm. in length, 35 to 50 

 mm. in diameter; externally blackish-brown, surface marked by 

 depressions, but otherwise smooth; hard, heavy and brittle, the 

 fracture being uneven; internally light brown to reddish-brown, 

 somewhat variegated from the fragments of contused seeds; odor 

 slight; taste astringent, bitter. 



Powder. Light pinkish-brown or dark brown; consisting 

 mostly of irregular masses made up of parenchyma cells contain- 

 ing more or less altered starch grains; unaltered starch grains occa- 

 sional, from 0.010 to 0.025 mm. in diameter, varying from spheroidal 

 and polygonal to ellipsoidal and broadly ovoid; occasional frag- 

 ments with narrow elongated sclerenchymatous cells, the walls being 

 thick, yellowish and non-lignified. 



If 0.001 gm. of powdered guarana is added to a slide, upon which 

 a drop of hydrochloric acid has been previously placed, and a drop of 

 gold chloride T. S. is added and the mixture allowed to stand for a 

 few minutes, crystals of caffeine gold chloride should separate in the 

 form of orthorhombic plates and needles, the latter usually occurring 

 in spheroidal aggregates and finally forming branching groups. 

 For microphotograph of crystals of caffeine gold chloride, consult 

 Kraemer's Applied and Economic Botany, p. 163. 



Microcrystals of caffeine may be obtained upon heating 0.001 

 to 0.005 gm. of powdered guarana on a watch crystal, the sublimate 

 being collected either upon a microscopic slide or another watch 

 crystal. (See also p. 436.) 



Constituents. Caffeine 2.5 to 5 per cent; tannin (catechu- 

 tannic acid) about 25 per cent; ash about 2 per cent. Guarana 

 also contains considerable starch, a small amount of catechin, a 

 volatile oil, an acrid, green fixed oil, and saponin. 



RHAMNACE.E, OR BUCKTHORN FAMILY 



A family of over 500 species, consisting of shrubs or trees, 

 often woody climbers, and rather widely distributed. The leaves 

 are mostly simple and stipulate, the flowers are small and regular, 

 and the fruit is a drupe or capsule. The twigs of some of the species 

 as Rhamnus cathartica, possess stout thorns, hence the name buck- 

 thorn as applied to this species and the family. Many of the plants 

 are characterized by the presence of methyl-anthraquinone deriva- 

 tives, which give a bright red color with solutions of the alkalies. 

 These derivatives are found in the medullary rays and distributed 

 among the parenchyma cells of the cortex. Some of the plants 



