WOODY FIBRE. 151 



the exact nature of the part which is capable of 

 being converted to these great purposes. In that case 

 you must have recourse to your microscope ; be- 

 neath which you may place a little tow, the threads 

 of which are separated, and float in water. At first 

 sight, with a weak magnify ing-glass, you will discern 

 no distinct organization in these threads ; they will 

 look like dark lines of about the thickness of a fine 

 human hair ; but if you bruise them and tear them 

 about in the water with the point of a couple of 

 needles, you will in time succeed in separating each 

 of the threads into a very considerable number of 

 exceedingly fine parts, which you may discern, by 

 increasing the magnifying power of your microscope, 

 to be transparent tubes, composed of a tough mem- 

 brane, and tapering to each extremity like bristles ; 

 these are glued together in bundles which constitute 

 the finest threads that are visible to the naked eye. 

 Their business is not simply to grow in the inside of a 

 plant, in order that man may pull them out and ap- 

 ply them to his own purposes; they have a far higher 

 and more important office to fulfil. It is they which 

 give strength and toughness to every part, and which 

 enable the stem and the leaf to wave about in the 

 breeze or to bend before the storm without breaking ; 

 they are placed as a sort of sheath all round such 

 tender parts as the spiral vessels, which are enabled 

 within their safeguard to perform their delicate func- 

 tions with certainty and security ; and, finally, it is 

 they which act as so many water-pipes to convey the 

 fluids of plants with rapidity from one part to^ano- 



