I.] GENERAL CHARACTERS AND STRUCTURE. i? 



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 

 suffice 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, 



