THE BRITISH OAK. 37 
are well marked. In a transverse section (across- 
grain or horizontally as the tree stands), they can be 
easily counted and the age of the tree ascertained— 
one ring for each year. In the centre is the pith, 1 
to 4 mm. in diameter, formed of small, thick-walled 
cells. The annular rings are slightly undulating, 
bending outwards between the medullary rays, which 
are of two kinds; one large, broad, and glossy, the 
other very numerous and small (see Plate II). Itis 
impossible to distinguish between the wood of the 
two species. 
“Oak wood makes excellent charcoal, especially 
for metallurgic purposes; the Sussex iron, formerly 
regarded as the best produced in Britain, was smelted 
with oak charcoal from the great woods of the adjacent 
weald”’ (‘ Encyclopedia Britannica,’ art. ‘“ Oak.’’) 
The bark is the most valuable part of the tree, and 
its value depends upon the amount of tannin it con- 
tains. The trunk and large limbs yield an abundant 
supply. In young trees the yield is about 8 per cent. 
of tannic acid; in old trees it is much less. Trees of 
thirty to forty years’ growth yield the largest per- 
centage. (. sessiliflora yields a larger amount of 
tannic acid than does Q. pedunculata. 
The flowers are monecious (7. e. both sexes on the 
same tree). The staminate or male flowers of each 
species are arranged in clusters on long slender fila- 
ments, and are known as catkins. The female or 
pistilate flowers are sessile in one species (from which 
it takes its specific name), and pedunculated in the 
other, and either single or in groups of two, three, 
or more. 
The leaves of each species are broad and deeply 
sinuated, the lobes being bluntly rounded. They are 
arranged on the twig in an alternate manner. Nor- 
mally they attain a length of 12 to 14 cm. and 7 to 9 
cm. at greatest breadth of blades. There is, however, 
considerable variation. A perfectly-formed mature 
leaf off a large tree may not exceed 3 cm. in length, 
