]04 PRINCIPLES OF GARDENING. [CH. II. 



two given soils or manures : the most fertile "vvill -be 

 the most absorbent and retentive. 



Some persons have argued that the moisture-re- 

 tentive powers of manures must be injurious to 

 plants, by withholding that moisture from their 

 roots; but these theorists argue without an acquaint- 

 ance with facts. Such manures have a greater at- 

 traction for moisture than is possessed by atmo- 

 spheric air ; but it is much less powerful than the 

 po\^er of suction possessed by roots. There is no 

 saline body which they will not deprive of the mois- 

 ture it has absorbed — nor \rill any be surprised at 

 this, when they know that the root of a pear-tree, 

 half an inch in diameter, absorbs water with such 

 force and rapidity as to cause mercury to rise up 

 an attached tube eight inches in sL\ minutes ^. 



Some manures increase the growth and \igour of 

 plants, by stimulating their absorbent and assimi- 

 lating organs. This will only be admitted by those 

 who, like myself, allow that plants are gifted with 

 sensation — a topic more fully discussed in a future 

 chapter ; but a few illustrative facts may be here 

 stated. The Venus 's fly trap [Dioncea muscipula) 

 has jointed leaves, which are furnished on their 

 edges with a row of strong pricldes. Flies, attracted 

 by honey which is secreted in glands on their surface, 



* Hale's Veg. Statics. Exp. xxi. 



