WOODY TISSUE. 



353 



4. Brown or gray, and in many cases bright red and 

 orange (apparently uniform to the naked eye), are found 

 to be compounded of other colours, as yellow, green, or 

 orange with violet, or green and red; bright red and orange 

 in like manner of blue-red with yellow or orange. 



5. Black, excepting in the bean, is due to a very deeply- 

 coloured cell-fluid. 



6. All the cells of an organ are rarely uniformly 

 coloured. 



7. The colour usually resides in one or in a few of the 

 outer layers of cells. 



8. The coloured cells are but exceptionally covered by 

 a layer of uncoloured ones. 



9. Combinations of colour are occasioned by diversely- 

 coloured matters in the same or in adjacent cells. 



The Woody tissue of plants is not without its interest, 

 it consists of elongated transparent tubes of considerable 

 strength : some are almost entirely made up of this 

 tissue. It is by far the most useful, and supplies 

 material for our linen, cordage, paper, and many 

 other important articles in every 

 branch of art. This tissue, re- 

 markable for its toughness, is 

 termed fibre, the outer membrane 

 of which is usually structureless. 

 In Flax and Hemp, in which the 

 fibres are of great length, there 

 are traces of transverse markings, 

 and tubercles at short intervals. 

 In the rough condition, in which 

 it is imported into this country, 

 the fibres have been separated, to 

 a certain extent, by a process 

 termed hackling. It is once 

 more subjected to a repetition of 

 hackling, maceration, and bleach- 

 ing, before it can be reduced to the 

 white silky condition required by the spinner and weaver, 

 when it has the appearance of structureless tubes, fig. 197 B. 

 China-grass, New Zealand flax, and some other plants, pro- 

 duce a similar material, but are not so strong, in conse 

 A A 



Pig. 196. 



Fibres of Silk. B, Fibres 

 of Cotton. 



