184 
UPON THE SUPPOSED ABSORBENT POWERS OF THE CELLULAR POINTS, OR 
SPONGIOLES, OF THE ROOTS OF TREES, AND OTHER PLANTS. 
BY THOMAS ANDREW KNIGHT, ESQ., E.R.S. * 
An opinion is very extensively, if not generally, entertained, that the nutriment 
which trees and other plants derive from the soil in which they grow, is exclusively 
taken in by the cellular extremities of their roots, which, from their texture, have 
been called spongioles ; and which, in their organisation, differ from other parts of 
the root in being totally without any alburnum or woody matter distinct from the 
bark. But it is through the alburnum alone of trees, as I have proved by a great 
variety of experiments, and as is, I believe, generally admitted, that the ascending 
sap, under ordinary circumstances, passes up from their roots into their branches 
and leaves ; and as this substance does not exist in the spongiole, my attention 
was directed to an inquiry whether the spongioles possess the power of transmitting 
fluids, and, if such power were found to exist in them, through what peculiar chan- 
nels such fluids pass up : and as these questions are necessarily interesting, and to 
some extent, in particular cases, may become important to the practical gardener, I 
communicate the result of my experiments. 
Spongioles are obtainable in the most perfect state from large seeds, such as 
those of the common or French bean, which have been permitted to germinate by 
simply detaching them from the cotyledons ; as they thus remain united to the 
caudex of the plant, and its bud and plumule. Many of these were obtained from the 
seeds of plants of several kinds, and subjected to various modes of treatment in soils 
of diff'erent qualities ; but all perished without a single plumule having expanded, or 
having apparently received any nutriment, either from the soil or other source. Yet 
the spongioles, in these cases, must have contained greatly more living organizable 
matter, derived from their cotyledons, than the whole body of the seed of a very 
large majority of plants can possibly contain : but they were, I conclude, incapable 
of transmitting it into the plumules, owing to the want of alburnum. 
I therefore believe my opinion, that spongioles are imperfectly organized parts 
of the plant, which neither absorb from the soil nor transmit fluids of any kind for 
the service of other parts of it, to be well founded ; but alburnous matter is gene- 
rated with great rapidity within them ; and they become to a very great extent 
transmuted into perfect roots long before the growth of the stem or branches of the 
tree commences in the spring, and by these newly formed roots (but not by these ex- 
clusively) I conceive that nutriment is absorbed from the soil and sent up into the 
leaves, to be there converted into the true sap of the plant. I am aware that the 
above stated opinions are in opposition to those of many eminent physiologists, to 
which much deference is due : but I think that they have erroneously included within 
their spongioles portions of alburnous fibre, a substance never found in the organ 
properly called a spongiole. 
* Read before the Horticultural Society, May 17, 1836. 
