INTERNAL STRUCTURE OF PLANTS. 
29 
But let us hear what Schleiden says respecting these things. 
In vain” (he says, in his inoffensive observations respecting 
the nature of the stomata, in Wiegmann’s Archives of Natu- 
ral History for 1838, vol. i. p. 57) “ have I tried to ascertain 
a fact, by which it might be rendered probable, that these 
secretions originate more from the exhalations of the alleged 
glandular cells, than from those of the other parenchymatous 
cells, especially from those which border immediately on the 
cavity into which the stomata conduct ; and it appears to me, 
that the alleged function, considering the present state of the 
science, is nothing but a mere petitio prmcip>iL For instance, 
let us take the Comferoe. Here I find resin on the stomata ; 
on removing this by etherical oil, the stomata exhibit a con- 
tinually increasing chasm. I next find beneath it a cavity, 
which (including the two curved cells) is surrounded by nothing 
but cells which contain gum, mucus, some starch, chlorophyll, 
but no trace of resin or turpentine ; on the other hand, I find 
large turpentine ducts much lower down in the parenchyma ; 
and I now conclude, that the volatile turpentine oil makes its 
exit from those ducts in the form of vapour, arrives at the 
intercellular cavities by following the intercellular ducts, and 
evaporates into the atmosphere through means of the stomata ; 
in doing which, according to its nature, it leaves a certain 
quantity of resin. This inference appears to me quite natural. 
But, on the other hand, if two of those perfectly equoi cells, 
filled with green matter, are arbitrarily chosen, and supposed 
to constitute glands which secrete resin, because they happen 
to be situated near the exterior, I really cannot see how 
this can be justified by any kind of logic.” I find the cells 
beneath the resinous covering of the Cistacece, and of many 
other plants, green ; and I cannot conceive how the oil of tur- 
pentine, vvdiich is alleged to make its exit from the turpentine 
ducts in the shape of vapour, can leave resin in the stomata. 
However, I am glad that my opinion is similar to that of my 
friend Berzelius. He has certainly been still more abused 
about it than myself, because he is a greater man than I am. 
In the “ Journal of Natural History and Physiology, by Van 
der Hoeven and I)e Vriese, Leiden, 1840,” we find, p. 185, a 
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