Special M orphology and Classification. 365 
_ with extremely small bordered pits (Fig. 14, p. 13). Even | 
when the latter are larger, they differ in size and form from 
those of the vessels which occur along with them. The 
FiG. 473. — Transverse section through the wood of the oak; H/’ thin-walled, 
Hf” strongly thickened wood-fitres; Hf parenchyma of the xylem; s fibres 
of the ‘silver-grain’; G” small vessels; adjoining G’ is a very large vessel, 
the size of which is only slightly indicated by the curved border-line. 
wood-cells of the inner spring-wood are, as a rule, much less 
strongly thickened than those of the outer autumn-wood 
(Fig. 479, p. 373). There is nowhere found in the wood-cells 
