52 Mr. ArthiLv Deane on 



several feet of Red Oak, even if unseasoned, because tyloses are 

 not present in the pores, but a pressure of 100 lbs. per square inch 

 is sometimes insufficient to force air through a single inch of 

 unseasoned White Oak, because the pores of this species contain 

 abundant tyloses. They thus tend to retard the introduction of 

 foreign fluids such as antiseptics. 



Wood Fibres. — These are thread-like cells, not unlike 

 tracheids in outline, but usually longer and with much thicker 

 walls, which is a characteristic feature. Sometimes they are so 

 thick as to show hardly any cell cavity, and they are devoid of 

 the characteristic bordered pits of the tracheids of softwoods, 

 the pits being small and slit-like. They are not found in soft- 

 woods, but they form the principal structure in hai'dwoods. 

 These fibres contribute largely to the strength and hardness of 

 hardwoods, and the more they predominate the better. 



According to E. C. Jeffrey a peculiar kind of fibre is found 

 in some Oaks and in some leguminous woods, caused by the 

 inner wall of the fibre becoming mucilaginous. Woods having 

 mucilaginous fibres are stated to be of special value in cabinet 

 work on account of their relative immunity from shrinking and 

 swelling, while the numerous mucilaginous fibres composing the 

 woods of False Acacia {Rohinia Pseudacacia) make the wood very 

 suitable for trenails in the construction of wooden ships, as they 

 neither swell unduly in water nor shrink in the sun. 



Wood Cells ( Wood parenchyma). These are much more 

 abundant in hardwoods than in softwoods Sometimes they are 

 scattered in characteristic fashion among the wood-fibres and are 

 usually lighter in colour than the surrounding tissue. They 

 often adjoin the vessels and become a useful aid in identifying 

 timbers. In the Oak they form radial lines in the summer 

 wood (Fig. 2), while in the Elm they surround the pores 

 to form tangential lines. In Corkwoods, such as Balsa wood 

 (Ochroma Lagopus) exhibited, the wood consists in a large part 

 of wood cells. The wood cell tissue of the sapwood is used 

 during the resting season as a storehouse for reserve food 

 material such as starch. 



