OAK TIMBER. 



137 



Medullary rays of two kinds, a smaller number of 

 very broad, shining ones, from to 1 mm., or even a 

 centimetre or more apart, and very numerous (about 



FIG. 38. Transverse section of wood of oak (magnified live diameters), 

 showing five annual rings, as denoted by the large vessels of the 

 spring wood ; the vessels become smaller in the summer and 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, fibers, and wood-parenchyma. 

 (MUller.) 



