Circulation in Vegetables. 99 



Art. XIII. — Circulation in Vegetables; by Prof. E. Emmons. 



The remarks in the following communication, are offered with 

 some reluctance, as most of them are in opposition to the com- 

 mon opinions of the day. The subject too is one attended with 

 difficulties, and investigations relating to it cannot result in the 

 clearness and certainty which are so desirable in one of so much 

 interest. The opinions advanced in this paper are not newly adop- 

 ted or taken up recently or, suddenly, but have been deliberately 

 formed and have been often expressed in my lectures on vegetable 

 physiology. I confess however that they have not been formed so 

 much from direct experiment as could be wished j they may there- 

 fore have little weight in the estimation of the public. But as 

 the subject is interesting, suggestions of any kind may not be lost, 

 as they may lead others more able than myself into a course of in- 

 vestigation, which, will result in discovering the true course of the 

 circulation in vegetables. Writers on this subject seem to have de- 

 sired to establish too much by analogy. They have studied the 

 functions of the different organs in animals and those functions they 

 have transferred to vegetables. Thus they make the leaves perform 

 the functions of the lungs, and they discover also in vegetables a double 

 circulation, notwithstanding there is not the vestige of a heart. There 

 are doubtless analogies between the two kingdoms, bnt they are of a 

 more general nature ; such for instance as the following. The dif- 

 ferent orders of animals feed on different kinds of food, and we might 

 infer what we already know, that different plants might require dif- 

 ferent kinds of soil. As climate has a controlling influence over ani- 

 mals, we might infer the same of vegetables. Different orders of ani- 

 mals are furnished with different kinds of apparatus for the circulation 

 of the blood ; so may the different orders of vegetables be thus diverse 

 in the mode of circulating their fluids. Such are the analogies which 

 it is safe to admit. But we may not compare the different parts of 

 vegetables with those of animals and say that their functions are 

 analogous, because the two kingdoms are not formed on the same 

 general plan. I shall now proceed with the subject by noticing, in 

 few words, the theory of Mr.. Knight of England, as given in the 

 Phil. Trans, for 1803. His theory may be stated concisely as fol- 

 lows, " water taken up by the roots of vegetables ascends principal- 

 ly through the central wood to the leaves, in which organs some of it 



