92 LIGNEOUS FIBRE. [LECT. III. 



elastic, semi-opaque filament, which, by its cohesion 

 with other filaments of the same kind., forms the 

 proper fibres, or layers of longitudinal fibres, that 

 constitute the grain or solid part of wood. It 

 enters, also, into the composition of another set 

 of layers, that traverse the longitudinal, named 

 divergent. It is intended to give support and 

 firmness to the vegetable body, and hence is found 

 in greater abundance in trees and other perennial 

 plants ; and according to the number of the ligneous 

 fibres in each bundle of layers and the force of 

 their cohesion, the wood of different trees possesses 

 a greater or less degree of hardness. But, 

 although wood is found of various degrees of 

 consistence, yet, as Count Rumford has suggested, 

 it is probable that the ultimate fibre is the same 

 in all plants*. 



Whether the ligneous fibre be of original forma- 

 tion similar to the muscular fibre of animals, or 

 condensed membranous or cellular texture, or an 

 obsolete obstructed vessel as Hedwig supposes, 

 is yet undetermined. It is so intimately united 

 with the cellular texture containing the vegetable 

 secretions, that it cannot be procured pure for 

 examination, without the aid of chemical agents to 

 separate these adjuncts. If a thin shaving of well- 

 dried wood be first digested in boiling water, then 



* Nicholson's Journal, vol. xxxiv. p. 319. 



