CHAP. II. 
ROOT. 
109 
others name them fibrils^ — a term more generally adopted ; 
while the terms rhizina and rhizula have been given by Link 
to the young roots of mosses and lichens. 
A fibril is a little bundle of bothrenchyma, or sometimes of 
trachenchyma, 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 
with great force, and has been called by De Candolle the 
Spongiole or Spongelet It must not be considered a particu- 
lar 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 epiphloeum, 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 it 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- 
bitaceae they are much smaller. When the root is divided into 
a multitude of branches and fibres, it is called fibrous : if the 
fibres have occasionally dilatations at short intervals, they are 
called nodulose. When the main root perishes at the extremity, 
it receives the name of prcemorse, or bitten off : frequently it 
consists of one fleshy elongated centre tapering to the ex- 
tremity, when it is termed fusiform (or tap-rooted by the 
English, di.ndi pivotante by the French)* : if it is terminated by 
several distinct buds, as in some herbaceous plants, it is called 
many-headed (multiceps). 
The roots of many plants are often fleshy, and composed of 
lobes, which appear to serve as reservoirs of nutriment to the 
* In the former editions of this work the turnip has been referred to a 
root. But, from the investigations of Turpin and others, there is no room 
to doubt that the turnip, the radish, the cyclamen, and the elephant-foot, 
are all distensions of the stem : either of the first internodium, or of the 
inferior prolongation of the stem below the cotyledons and above the 
root. 
