BOTANIC MATERIA MEDICA, 159 
grains, given in form of an infusion. The sa- 
ponin is said to be an active poison. There is 
one officinal preparation of the bark; a tinctura. 
Quercus Tinctoria, Black Oak.—Natural 
order Cupuliferee. Commonly known as the red 
oak. The varieties of this species make up a 
large proportion of our forest trees. Whilst the 
white and black oaks are the only two which are 
recognized in materia medica, these differ in 
many respects from the European variety. It 
is said the guercus nigra or black jack and the 
guercus falcata or Spanish oak are often used as 
adulterents of the officinal black oak bark. Like 
the white, the red oak bark contains a large 
amount of tannin, pectin, and guercitrin; the 
latter constituent is a yellow crystalline sub- 
stance, nearly tasteless, and when added to a 
solution of iron, coloring it green, yielding, with 
dilute acids, two radicles, called respectively 
isodulcit and quercitrin. The black oak bark, 
when deprived of its corky layer, is of a brick- 
red brown color, + of an inch (5 millimeters) in 
thickness, with many fissures. When broken, 
the fracture is coarsely fibrous, the taste bitter 
and astringent, with an odor of tan bark. The 
dose of the bark is 15 to 60 grains (1 to 4 grams) 
in form of aninfusion. Rarely prescribed; used 
as a poultice in indolent ulcers, It is not often 
used in the tanning of leather, as it is said to 
give an undesirable color. 
Quercus Alba, White oak.—Natural order 
Cupuliferee, This well-known variety of the 
oak is a native of the North American woods. 
The flowers are divided into the fertile and un- 
fertile; the former are clustered or somewhat 
