WOODY FIBRE. 



19 



from the root upwards ; and, lastly, to the deposit on the inner side of the membrane. 



This sentiment is irresistible, when we remember the various economic purposes 



to which man in all ages has applied the 

 wood of forest trees, and also the power 

 of resistance and elasticity which trees are 

 required to offer while supporting large 

 branches at a considerable angle, and to 

 prevent their being uprooted or broken to 

 pieces by violent storms, all of which is 

 mainly due to the tissue now under con- 

 sideration. 



There are two kinds of woody tissue 

 viz., the plain and the glandular. The 

 plain we have already described. The 

 glandular is that form which more nearly 

 resembles bothrenchym, and indeed may 

 easily be mistaken for it. It consists of a 

 plain fibre or tube, such as that already 

 described ; but, in addition, there is super- 

 imposed, with great regularity, a series of 

 rounded translucent bodies called, or rather 

 their m i sca lled, glands (Fig. 56). These are, for 



Fig. 54. Bundles of 

 woody fibre of the 

 flax plant fJMnim), 

 considerably mag- 

 mfied - 



de p 0s it and 



pointed extremities , -., 



overlapping each the most part, arranged in single rows, and 



other< are so large as to occupy the whole face 



of the fibre. 



There is great difference of opinion as to the nature of these so-called glands ; 

 some authors regarding them as simple concavities in the nature of a simple pit, whilst 

 others believe that there is a pit, and in that pit is deposited the rounded, flattened 

 body termed the gland, or bordered pore. 



Professor Quekett adopts the opinion that these bor- 

 dered pores lie in concavities between two adherent fibres 

 (Fig. 57). The bordered pore is hollow, and biconvex, so 

 as to fit into the two cavities. They are best seen in a 

 section of wood, taken parallel to the medullary rays. 



It is not a little remarkable that this form of woody 

 fibre should be found only in one class of trees viz., the 



Conifer ce, or fir tribe, with their allied genera ; and in such Fig. 56. Section of common fir 

 plants it is the only form of woody tissue met with. If 

 a very thin section of a piece of fresh fir tree, or of a piece 

 of deal or cedar, be examined with the microscope, as before 

 directed, the glands will be seen very distinctly (Fig. 56) ; 



and if a piece of rotten fir be selected, it will not be difficult to find a spot at which the 

 gland appears to have fallen out. Such also is the case with the coal shale, a large 

 portion of which is composed of the stems of the fir tribe, which have been buried 

 during thousands of years ; and if care be taken to grind down a thin section, not only 

 may the glands and their remains be seen, but in some instances the pits which once 

 contained the gland. 



This, however, is chiefly a matter of curiosity, since we do not know anything of 



wood, or deal; showing the 

 pointed extremities of the 

 woody fibre and the gland, or 

 bordered pores, in a single 

 row on each fibre. 



