TISSUES. 



structure, for some generally included under these de- 

 finitions run very closely indeed into certain modifica- 

 tions of vascular tissue. 



14. Fibrous tissue, or woody fibre, as generally under- 



stood, consists of thin long mem- 

 branous tubes adhering together 

 in pretty close fascicles : the size 

 of the fibre varies in circumference 

 and length, and is generally coni- 

 cal or accuminate at its apices. 

 The surface of fibre though mostly 

 even is not always so, but presents 

 irregularities which are caused by 

 the pressure of other structures 

 upon it ; and the fibre, though 

 generally hollow all the way down, 

 sometimes seems hollow only at 

 intervals, and often becomes con- 

 siderably dilated there. 



15. Though woody fibre is generally devoid of all 

 . 4 marks upon its surface, in some plants 



it presents very peculiar appearances in- 

 dependently of any thing resulting from 

 pressure of contiguous bodies. These 

 appearances, the nature of which it is 

 exceedingly difficult to determine, are 

 well seen in the tribe Coniferse or pine 

 family, some looking upon them as pores, 

 others as thinnings, and some as bodies 

 adhering to the fibre. The most pro- 

 bable view appears to be that they are 

 depressions in the walls of the fibre, the 

 centre of which depression is either po- 

 rous or else thinner than any other por- 

 tion. It often appears as if something 

 were lodged in these depressions. 



