OAK TIMBER 137 
Medullary rays of two kinds, a smaller number of 
very broad, shining ones, from 4 to 1 mm., or evena 
centimetre or more apart, and very numerous (about 
Fic. 38.—Transverse section of wood of oak (magnified five 
diameters), showing five annual rings, as denoted by the 
large vessels of the spring wood; the vesse]s become 
smaller inthesummerand autumn wood, and are arranged 
in tongue-like groups. Nine broad medullary rays are 
shown, the rest are very narrow (cf. fig. 27). The rest 
of the section is filled with tracheids, fibres, and wood- 
parenchyma, (Miiller.) 
