1.] GENERAL CHARACTERS AND STRUCTURE. 17 



continuous as they pass out of the cambium stage. 

 Between these vessels are much more numerous 

 elements with very small lumina and thick walls : the 

 latter are the wood-fibres proper, and have to be tech- 

 nically distinguished from the apparently somewhat 

 similar wood-tracheides of the pines, firs, &c. Each fibre 

 is, in effect, a tracheide with much thicker cell- walls 

 than usual, and devoid of the characteristic '' bordered 

 pits " referred to when speaking of those structures : 

 it is essentially a tough, strengthening element. Here 

 and there, scattered in small groups, are certain rows 

 of shorter cells, which, however, are not very numerous 

 in the beech : they are called wood-parenchyma (Fig. 

 6, wp?), and occur particularly in the vicinity of the 

 vessels. These wood-parenchyma cells are produced 

 by the cambium-cell becoming divided across into 

 several superposed short chambers, which retain their 

 living contents : they resemble the cells of medullary 

 rays in nearly all respects. 



It is beside the purpose here to describe in detail 

 the histology of the beech-wood, and reference may 

 be made to the figures for further particulars. It may 

 sufiSce to point out that all the elements— cells, fibres, 

 and vessels — are formed as before by the gradual 

 development of cambium cells ; and the same is true, 



C 



