192 CONSERVATIVE ORGANS. [LECT. V. 



All subterranean roots assume a particular di- 

 rection ; which is constant in every individual of 

 the same species of plant. They are said to be 

 perpendicular (perpendicular is) when the caudex, 

 or main body of the root,, extends perpendicularly 

 into the ground, as exemplified to the majority of 

 fusiform roots (p. 130), and in the main or top 

 root of most trees : and horizontal (horizontalis) 

 when the extension is nearly parallel to the plane of 

 the horizon, so that the root forms nearly a right 

 angle with the stem or herbaceous part of the 

 plant ; as, for instance, in Winter Green, Pyrola 

 umbellata, Sweet Flag, Acorus calamus, and in 

 the majority of the articulated roots. Many of 

 the horizontal roots, whilst they run under the 

 surface of the ground, push up stems at intervals 

 so as to multiply the plant ; tnence the appellation 

 creeping roots (R. repens) : as in common Spear 

 Mint, Mentha viridis ; Couch Grass, Triticum 

 x. repens ; Bulbife- 



rous Coral Wort, 

 Dentaria bulbife- 

 ra(fig.x) 9 and ma- 

 ny other plants. 

 And this proper- 

 ty renders some 

 weeds extremely 

 obnoxious to the 

 farmer : for, if any portion of a creeping root be 



