THE ROOTS OF VASCULAR PLANTS. 217 



differ but little from that of the stem, yet they present, 

 in their extreme ramifications, a structure which is 

 peculiar to them. They are completely devoid of the 

 fiat appendages of the stem which are known by the 

 name of leaves ; and most of them ramify, either laterally 

 or by their extremities, into a multitude of very minute 

 fibrils, which collectively constitute the Chevelu. Roots 

 are said to be fibrous when they have many slender 

 branches, and this term is especially used in contradis- 

 tinction to tuberous ones — that is to say, those which 

 have distinct swellings in some part of their length. 



The trunk and principal branches of the roots of 

 Exogens are in the form of an elongated cone, the point 

 of which is directed to the part most distant from the 

 neck. Their increase in size differs but little from that 

 of stems. The chevelu is formed of a multitude of very 

 minute little fibrils, which appear cylindrical ; they 

 arise without any fixed order, especially where there is 

 the least stagnation of juice. It is sufficient, for exam- 

 ple, to cut off the extremity of a radical branch to cause 

 a chevelu to be formed there. 



The history of this kind of fibrils is as yet but little 

 known, its subterranean position rendering observation 

 difficult. Some, considering the chevelu as almost a 

 peculiar organ, believe that it falls off each year, and is 

 afterwards reproduced ; but if it be possible that it dies 

 and is destroyed, it is scarcely probable that it falls off 

 in the strict sense of the word, for it has no articulation 

 at its base. Others have thought that it only differs 

 from the common branches of the root by its minuteness 

 and multiplicity ; that all its fibrils are equally suitable 

 for being transformed into radical branches, but from 

 the great number of them which are produced, there are 

 only some which are thus developed, and that the others 

 die more or less rapidly. This opinion, founded upon 



