86 ORGANOGRAPHY. BOOK I- 



appendages ; neither do they ever indicate upon their surface, 

 by means of scars, any trace of such : all underground bodies 

 upon whicli scales have been found are stems, whatever they 

 may have been cailed ; the only appendages roots ever have 

 arc such things as the little hollow floating bladders found in 

 Utricularia. A fourth distinction between roots and stems is, 

 that the former have never any stomates upon their cuticle ; 

 and, finally, in Exogens the root has never any pith. It has 

 been also said that roots are always colourless, while stems are 

 always coloured ; but aerial roots are often green, and all un- 

 derground stems are colourless. 



The body of the root is sometimes called the caudex ; the 

 minute subdivisions have been sometimes called radicules, — a 

 term that should be confined to the root in the embryo ; 

 others name them Jib7'ils, — a term more generally adopted ; 

 while the terms rhizina and rhizida have been given by Link 

 to the vovuiGj roots of mosses and lichens. 



A fibril is a little bundle of annular ducts, or sometimes of 

 spiral vessels, encased in woody fibre, and covered by a lax 

 cellular integument: it is in direct communication with the 

 vascular system of the root, of which it is, in fact, only a sub- 

 division ; and its apex consists of extremely lax cellular tissue 

 and mucus. This apex has the property of absorbing fluid 

 witli great rapidity, and has been called by De Candolle 

 the Sporiffiole or Spongelet. It must not be considered a par- 

 ticular organ ; it is only the newly formed and forming tender 

 tissue. In Pandanus the spongelets of the aerial roots consist 

 of numerous very thin exfoliations of the epidermis, which 

 form a sort of cup fit for holding water in. 



The proportion borne by the root to the branches is ex- 

 tremely variable: in some plants ic is nearly equal to them, 

 in others, as in Lucerne, the roots are many times larger and 

 longer than the stems ; in all succulent plants and in Cucur- 

 bitaceas they are much smaller. When the root is divided into 

 a multitude of branches and fibres, it is caWeA Jihrous : if the 

 fibres have occasionally dilatations at short intervals, they are 

 called nodidose. \Vlien the main root perishes at the extremity, 

 it receives the name of prcB morse, or bitten off: frequently it 

 consists of one fleshy elongated centre tapering to the ex- 



