^66 
QUERCUS ROBUR. 
ni«e in carpentry ; and its superior excellence for the purposes of ship 
%uilding,^has long rendered it an object of national importance. 
Oak saw-dust id one of the most valuable of our indigenous vege- 
tables, used by dyers for dyeing cotton cloths of a drab colour, the 
<iifferent shades of which are made by this substance, variously 
managed. The oak apple is likewise used for the purposes of dye- 
ing, and the bark is in universal use for the purposes of tanning 
leather. 
The trunk and branches of this tree are covered with a rough 
brown bark ; the leaves are alternate, and stand upon short petioles, 
oblong, deeply sinuated, forming obtuse lobes : on the upper sur- 
face of a deep shining green, underneath paler, and nearly glau- 
cous ; the flowers, which appear in May, are male and female upon 
the same tree, and are produced in axillary catkins ; the male is lax, 
pendulous, and many-flowered; the female larger, peduncled, and 
three-flowered ; the calyx of the male flower is of a yellowish colour, 
membranous, bell-shaped, and divided into five, six, or seven pointed 
segments ; the stamens are t^n, longer than the calyx, and support 
large double anthers. The calyx of the female flower is coriaceous, 
scaly, and downy ; the germen is ovate, the style short, and sup- 
ports three permanent stigmas; the fruit is an oblong, coriaceous, 
smooth nut, about an inch and a half long, and is well known under 
the name of acorn ; it is fixed into the calyx as in a shallow cup, 
but dropping from it when perfectly ripe. The fruit ripens in 
October. 
Sensible and Chemical Properties. Oak bark is inodo- 
rous; its taste is rough, astringent, and accompanied with some 
degree of bitterness : these qualities it yields both to water and 
rectified spirit. The watery infusion is acted upon by all those agents 
which aff'ect the infusion of galls, and which indicate the presence of 
tannin, extractive, and gallic acid. (See Chemical Properties, &c. 
of galls.) M. Vauquelin has discovered a remarkable chemical 
difference between oak bark and gall nuts, the latter precipitating 
tartrate of antimony and infusion of cinchona, but which are not 
acted upon by the former : we are told however by Dr. Thomson, 
that " infusion of oak bark forms a precipitate with infusion of yel- 
low cinchona bark." According to the analysis of Sir H. Davy, one 
ounce of the inner cortical part of young oak bark afforded by 
lixiviation. 111 grains of solid matter, of which 77 were tannin; the 
middle coloured part, or cellular integument, yielded only 43 grains 
of solid matter, of which 19 were tannin ; and the epidermis fur- 
nished a very small portion either of tannin or extractive. The 
