THE COURSE OF THE SAP IN PLANTS 
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phenomena of purely vegetative life. Electricity (be its essence, as an emanation from Creative 
Power, what it may), is everywhere, in every particle of matter, and always in action when moved 
even by the faintest breathing that could disturb the cobweb’s fibre ! Electricity attracts, and then 
induces an opposing condition, which produces the appearance of repulsion. Let the atmosphere be 
in an active, or as it is termed, positive state, the fluids prepared in the soil are then attracted, and 
drawn upward through the sap-vessels ; at the same time, a contrary, or negative state being induced 
in the ground, those fluids appear to be driven or propelled by a force setting toward the roots, and 
thus far may justify the theory of propulsion. Reverse the conditions, and the effect will be a change 
of the action in the vitalized fluids. 
So far, electricity appears to furnish us with sound general data ; but we cannot attain the minutiae 
of active forces. Such understanding and knowledge are too high and wonderful for us !! 
•“If,” continues Prof. Henslow, “ Mr. Beaton had cut away the two buds at the end of this Vine- 
branch,” (see extract above alluded to, as at p. 117, Gardeners’ Chronicle ,) “he would have found it 
filled with sap notwithstanding such mutilation; and if he had taken a portion on a perfectly dry 
branch, held it vertically, and poured water upon the upper cut surface, this would have been imbibed, 
and have ultimately passed through, and dropped out at the lower end. It cannot be assumed as an 
axiom, that the sap descends, as well as ascends in the way he describes; for trees are not transparent, 
and we cannot see this to be the case. We must test the fact by experiment, and his experiment is 
not sufficient for the purpose.” 
Here we may refer the reader to the late article on the descent of the sap, for the facts adduced on 
the authority of the late Mr. Knight, which appear to comprehend all that has come under the ob¬ 
servation of the keenest microscopic investigator. Those facts I find supported by the following 
remarks of Professor Henslow. “ But allow the branches to be filled as you will with crude sap, then, 
by exhalation through the stomata” (pores in the leaves) “ a large amount of the water is carried off, 
leaving what is held in solution in the remainder of the water. The stimulus of light, acting on the 
cellular tissue of the leaves, enables those parts to concoct the organic compounds—sugar, gum, &c., 
which are soluble in water, and are capable of being transmitted through the membranes of the cells, 
into the same spaces that are occupied by the crude sap. Thus, a general diffusion of such organic 
compounds throughout the plants takes place; this diffusion has been termed the ‘ descent of the sap.’ ” 
In few words then, we may safely conclude that the course of the sap is first from the roots up¬ 
wards, by a direct ascent through the sap-cells of the alburnum, or green annual layer of wood in 
trees; and in herbaceous plants through appropriate representative tissues, till it enters and pervades 
the leaves, wherein the processes of transpiration and of laboration are carried on ; that thence, the 
prepared fluids are conducted downwards, partly as the matter of Cambium (proper juice—the Indusium 
of Main), whence, the Liber or fresh layer of Bark is organized, and with it, the newly secreted por¬ 
tion of the medullary processes that converge horizontally toward the pith, and which form the 
silver grain of trees and shrubs. 
Therefore, that there is no simple movement of descent from the summit to the roots, or one of 
circulation-—-of flow and return, whatsoever; although, as Mr. Knight asserted many years ago, that 
there may be a commixture of the raw ascending sap, with portions of the laborated fluids that 
have “ sunk into” the horizontal medullary tissue, which is found in every part of the stem ; and by 
which the several layers of wood, however aged a tree may be, are preserved firm so long as vitality 
and health are supported. 
Some persons have endeavoured to establish a theory of the “ descent of the sap,” by the irregular 
healing of wounded bark ; first and chiefly—as they say—at the uppermost edge of the wound ; but 
this is met at once by the fact that wounded bark and abraded surfaces of the wood, do not so heal 
of necessity; much depending upon arbitrary circumstances, and the nature and extent of the injuries. 
Observation must convince every careful impartial person that such is the case; and, that in numerous 
instances, the cortical matter comes “ rolling over” in every direction pretty much alike, and some¬ 
times most extensively on the lower edges. I conclude this paper with the following interesting pas¬ 
sage from Prof. Hen slow’s article :—“ I do not suppose that gravity has much to do in affecting the 
question at issue. Unless my memory fail me, it has been proved that the upper edge of a wound on 
a ‘ ringed’ branch, when purposely bent downward in order to test this point, has been found to form 
a larger amount of new tissue than the other edge, (though this latter was now uppermost in position). 
If a wound on the trunk of the tree bear a small proportion to the whole surface, we might also 
expect very little or no difference between the amount of matter formed on different sides of the 
wound.” And, such is indeed the result, as careful observations made on almost any hedge-row elm- 
trees will verify. 
