98 PECULIAR JUICES. 



Emily. Then should we not feel the infliction of the 

 wound, although we might escape the smarting of the 

 blisters ? 



Mrs. B. The instrument is so minute and delicate, 

 that the wound it inflicts would not be felt were the skin 

 not inflamed and blistered by the poison. 



The nectar of flowers, the bloom of fruits, and the vi- 

 cious coating of aquatic plants, which preserve them 

 from the element in which they grow, may all be con- 

 sidered as excretory secretions ; but we will postpone 

 their examination till we enter upon the subject of flow- 

 ers and fruits. 



We have now traced the sap, from its first entrance 

 into the roots, throughout the whole frame of the plant ; 

 we have examined its component parts, the chemical 

 changes it undergoes in the leaves, its subsequent de- 

 scent under the form of cambium, and the various pecu- 

 liar juices which are secreted from this nutritive fluid, as 

 it returns from the extremity of the leaves into the roots. 



Emily. But is the whole of the sap consumed in the 

 performance of these several operations, and does no part 

 of the cambium return through the roots into the earth ? 



Mrs. B. It is the opinion of M. De Candolle, found- 

 ed on experiments he has made on this point, that a 

 small residue of the cambium exudes from the roots into 

 the ground. 



In planting, it has long been observed that trees of a 

 different species from those which previously occupied 

 the ground, thrive better than a repetition of those of the 

 same kind : whence it is inferred that the exudation of 

 one species of plant, though it may injure the soil for 

 other individuals of the same species, may possibly afford 

 appropriate nourishment for plants of another descrip- 

 tion. But this is a question we shall refer to at some 

 future period. 



Having now concluded our examination of the struc- 

 ture of a plant, and of the mode in which it is nourished, 

 I shall proceed next to observe in what manner it is af- 



542. Why might we not feel the wound, although we escape the effects 

 of the poison 1 ? 543. What is said of the nectar of flowers, the bloom 

 of fruits, and the viscous coating of aquatic plants'? 544. Does any 

 part of the cambium return through the roots into the earth 1 ? 545. 

 What has been long observed in the planting of trees'? 546. What rea- 

 son is assigned for this! 547. Of what subject is Mrs. B. next to treat? 



