92 ON CAMBIUM. 



Mrs. B. There is, it is true, a considerable analogy 

 between the animal and vegetable secretions : they are 

 both drawn from the general nutritive fluid, and each by 

 the means of glands ; but, owing to the extreme minute- 

 ness of the organs of plants, the vegetable anatomy is very 

 much behind that of the animal kingdom. 



Emily. In small herbs this must necessarily be the 

 case ; but in large forest-trees, I should have supposed 

 that the organs, when fully developed, would have been 

 of greater magnitude than those of animals. 



.Mrs. B. No ; the organs of the oak are not larger 

 than those of the family of mosses. Nor is this singular, 

 if you consider that the leaves and fruit of forest-trees are 

 not, in any respect, proportioned to the size of the plant: 

 you do not forget the fable of the Pumpkin and the 

 Oak. Every leaf and every flower must contain a system 

 of organs, adapted to the various operations it has to per- 

 form, without any reference to the general size of the 

 plant. In the animal economy we are still unable to dis- 

 cover the mode in which the glands elaborate their secre- 

 tions from the blood : how much less, then, can we ex- 

 pect to penetrate the secret, in a system where the organs 

 themselves are frequently so minute as to elude our sight, 

 the largest not being more than one-twentieth of a line in 

 diameter, and there are some, so small as not to exceed 

 the one-hundred-and-fiftieth part of a line in dimen- 

 sion ! 



Many ingenious hypotheses have been proposed to ac- 

 count for the secretory action of the glands, both in the 

 animal and vegetable economy, but none have hitherto 

 proved satisfactory. That which appears least objection- 

 able, is the agency of electricity ; but it must be owned 

 that the chief argument in favor of this agent is, that we 

 are not yet sufficiently acquainted with its powers to 

 prove the hypothesis which rests upon it to be erroneous. 



The chemistry of vegetables, on the other hand, is more 

 advanced than that of the animal kingdom ; because the 



501- What does Mrs. B. say of the analogy between the animal and 

 vegetable secretions'? 502. What is said of the comparative size of 

 organs in different vegetables'? 503. What is it said that every leaf 

 and every flower must contain 1 ? 504. Why are we not to expect 

 understanding the mode of elaborating secretions in vegetables'? 505 

 -What is the largest and what is the smallest of their organs'? 506 

 What hypothesis of secretory action appears least objectionable'? 



