20 



USES OF WOODY FIBRE. 



the especial functions of this kind of woody tissue. The botanist, however, attaches 

 value to it, since it enables him to demonstrate, in recent and fossil woods, the^exist- 

 ence of the Conifora, or fir tribe of plants. 



It is not uncommon to find a spiral fibre associated with this glandular structure, 

 and sometimes, as in the yew (Taxus baccata, Fig. 60), there are two which are wound 



Fig. 57. Fig. 58. Fig. 59. Fig. 60. 



Fig. 57. A lateral view of two adjoining fibres to show the concavity in each, and the space 

 formed by both for the reception of the bordered pore. B, bordered pores from the Salisburia adian- 

 llfolia, which are naturally found in cavities similar to those in A. 



Fig. 58. Similar arrangement of tubercles and cavities of the Aporum anceps. A, a fibre with 

 the tubercles or glands in situ, and projecting. D, the glands detached. C, the concavities on one 

 fibre whence the glands have been removed. B, the spaces for the lodgment of the glands formed 

 by two adjoining fibres. 



Fig. 59. Rows of bordered pores on the woody fibre of a fossil member of the fir tribe, which 

 had been long buried in the State of Ohio. 



Fig. 60. Porous woody fibre in the yew (Taxus baccata), with the spiral fibres wound in opposed 

 directions. 



in opposite directions, and give the appearance of a net- work. This is presumed to 

 assist in maintaining the patency of the tribe. 



The uses of woody fibre are very varied, and most important, and may be divided 

 into two categories, 1st, such as benefit the plants ; and 2nd, such as benefit man, 



1st. Such as benefit the plant. 



It is the chief organ of the circulation in all wooded plants, and for this purpose 

 pervades the plant from the root to the branches, and even to the minutest leaves and 

 flowers. The current in this tissue is slow and uninterrupted, and is directed upwards 

 from the shoot through the stems to the leaves, and downwards from the leaves through 

 the bark to the root. Thus its current has a twofold direction ; the ascending and chief 

 one being for the purpose of taking the raw sap from the ground, to be digested in the 

 leaves, and the descending being devoted to the removal from the leaves of the digested 

 sap, to be applied to the purposes of the plant, and also of the refuse matter to be car- 

 ried to the roots, and thence thrown out into the soil as a noxious material. These 

 functions are carried on more vigorously during the spring and summer seasons; but 

 it is probable that even in the depths of winter it does not cease. 



^ Another function of woody fibre is to be the store-house of the perfected secretions. 

 It is well known that as trees advance in life, the wood assumes a darker colour, and 

 more particularly that lying near to the centre of the stem. This is due to the deposit 

 of the perfected juices in the woody fibre at that point; and when age has matured the 

 tree, it is probable that the woody fibre so employed is no longer fitted for the circu- 

 lation of the sap ; and also, that the perfected sap, when once deposited, does not again 



