58 VEGETABLE ORGANOGRAPHY. 



improperly, New Zealand Flax. This tenacity has been 

 measured by Labillardiere, by suspending weights to 

 filaments of a fixed diameter ; by this method he found 

 that a thread of silk could support a weight of 34, 

 Fhormium tenax 2S7;, Hemp 16|, Flax 11|, and Aloe, or 

 the Agave Americana, 7. 



We often use the word Jibre as a convenient abbrevia- 

 tion to express a bundle composed, in vascular parts, of 

 vessels and elongated cellules, and, by analogy, in cellular 

 parts, simply of elongated cellules — forming a bundle 

 distinguished from the rest of the tissue by its greater 

 tenacity. The veins of leaves are only fibres more or less 

 ramified, which, in separating from one another, leave in 

 the cellular tissue interposed between them, a space 

 for its development. 



Dutrochet gives to the name Fibre a sense a little 

 different from the preceding : he says, that it is a 

 rectilinear assemblage of articulated cellules, or of elon- 

 gated cellular tissue ; he adds, that these cellules are 

 extremely small ; that, therefore, Fibres are modifications 

 of the cellular tissue, constituting distinct organs, which 

 draw up colovu'ed water, and convey the sap. This 

 definition of Dutrochet would apply well enough to the 

 veins or fibres of cellular plants ; but it has always ap- 

 peared to me, (and I believe that I am in accordance 

 with all other observers,) that the fibre of vascular plants 

 is composed of vessels and cellules intermixed. 



It suffices for the present to conclude that a Fibre 

 is not a simple organ, but a bundle composed, in the 

 majority of cases, of vessels and elongated cellules 

 firmly united into bundles; or solely of elongated cellules. 

 It is in the longitudinal direction of the fibres that the 

 course of the juices, especially the ascending, is directed. 



When several fibres are distributed circularly around 

 an axis, either real or ideal, the collection of them 



