Circulation in Vegetables. . 99 
Art. XII.—Circulation in Vegetables; by Prof. E. Emmons. 
Tue 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; 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 aheart. 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. Asclimate 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 forthe 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 
Sievert 
