86 STRUCTURE AND DISTRIBUTION OF ROOTS. 



root-fibres from any part ; as is shown, by breaking off a slip of 

 a branch and sticking it in the ground ; when if properly attended 

 to, it will usually form roots for itself, and soon become a new 

 plant. But it is more rare to find the roots capable of forming 

 leaves and flowers ; this, however, is the case in some instances, 

 such as the Maple a tree which may be completely inverted, 

 the branches being buried in the ground, and the roots spread 

 forth into the air, without being destroyed. 



114. The structure of the root- fibre, and of the spongiole 

 which terminates it, may be beautifully seen in the common 

 Duckweed; in which a single such fibre hangs from the under 

 surface of every leaf, for whose nourishment it is destined. On 

 looking at it with a magriifying-glass, or microscope, a dark line 

 is seen along its centre ; this consists of the bundle of vessels, by 

 which that part is occupied. These are enclosed in a firm sheath 

 of cellular tissue ; and at the point, this tissue is observed to be 

 softer, more spongy, and less regularly formed. The extremities 

 of the fibres are often seen to be covered with a little cap, that 

 corresponds with the cup which the aerial roots of the Pandanus 

 have been spoken of as possessing (. 110). 



115. The wide-spreading roots of a forest- tree do in reality 

 consist but of bundles or collections of such fibres, strengthened 

 by woody structure resembling that of the stem, and arranged in 

 the same manner. The structure of the v oody roots corresponds 

 mainly with that of the stem ; being Exogenous in Exogens, 

 and Endogenous in Endogens (Chap, v.) ; but in the former no 

 pith exists in the roots, their centre being occupied by vessels. 

 The spread of the roots from the stem, is usually greater than 

 that of the branches ; so that the rain which is prevented by the 

 latter from falling direct upon the ground, is directed just to 

 that part through which the root-fibres are distributed, ready to 

 suck it up. 



116. The force with which the roots absorb fluid is very 

 considerable. If a Vine be wounded in the stem, when the sap is 

 rising in the spring, a large quantity will flow out, and will con- 

 tinue to do so for some time. An Elm tree, from which a 

 portion of the bark and outer layers of wood had been accident- 



