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). It is 

 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 " (' Encyclopaedia 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 limits 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 

 thirt}^ to forty years' growth yield the largest per- 

 centage. Q. sessiliflora yields a larger amount of 

 tannic acid than does Q. pedimcidata. 



The flowers are monoecious (/. 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 bluntl}^ 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, 



