62 ?HE OAK 



the true fibres and tracheids ; they occur in those parts 

 where masses of true fibres abut on the groups consist- 

 ing of vessels and tracheids. They resemble tracheids, 

 but have very few and small, scarcely bordered, oblique, 

 slit-like pits : every stage can be detected between these 

 and true fibres. They must be looked upon as, so to 

 speak, abnormal, because their numbers are small com- 

 pared with the typical elements among which they 

 occur. 



The wood-parenchyma consists of vertical groups of 

 short cells, each group having the fusiform shape of a 

 tracheid (fig. 16, w.p) : hence the upper and lower cell of 

 each group has a pointed end. Each group obviously 

 arises from the transverse divisions of a long, prismatic 

 cell, pointed at both ends a cambium cell. The trans- 

 verse section is round, and somewhat larger than that of 

 a tracheid, and the walls are somewhat thinner. Where 

 they abut on vessels and tracheids their walls have 

 bordered pits, but where they stand in contact with 

 similar groups, or with parenchyma rays, the pits are 

 simple. During periods of rest they are loaded with 

 starch grains. 



The length of the groups i.e. of the fusiform cells 

 cut up into short cells varies ; the shorter ones have 

 only one transverse division. 



The wood-parenchyma is less abundant than the 

 tracheids and fibres, and predominates in the UK TO 

 vascular parts; after two to four or more fibres in a 

 radial row a single parenchyma cell may often be seen, 



