CHEMICAL AND MICEOSCOPICAL INVESTIGATIONS. 
25 
action of weak caustic liquor, then of dilute acid, present when acted on with chlorine water, the charac- 
teristics of ligneous cuticle of MM. Ererny and Terreil,* leaving a residuum which dissolves and blackens 
in sulphuric acid, and which is, I suppose, the incrusting substance of M. Payen, not showing a trace of 
alkaloid. How, then, can these fibres be the seat of the alkaloids ? 
Crystals from the Sap. 
I have said that the sap is peculiar, but I do not find in cutting across the stem of young plants of the 
species any visible appearance in the abundant sap to distinguish it at first from the juice of other plants. 
It so happens, however, that in the dried barks rich in alkaloids which I examine, I find salts generally, if 
not always, in a state of granulation, or I might even say, of such crystallization as is to be expected from 
the kinates of these alkaloids, which, as is well known, are of a very soluble nature. This appearance, as 
seen under the microscope, is shown in the third Plate of the present volume. In the lied bark we find 
the kinovates much more abundant; also the occurrence of those very marked and peculiar crystals 
which are represented in my first Plates, and which I have before abundantly described. I have no 
thought that any deduction can be drawn from them other than that which I have given, and certainly 
not that any practical conclusion can thence be deduced as to the goodness of the bark. 
My German friends naturally enough inquire how it is that they cannot find crystals which I see, and 
which our most skilful English draughtsmen find no di ffi culty in delineating. I have had the pleasure of 
showing those who have visited me the whole of my process, and convincing them by ocular demonstration 
that these crystals exist. The mode I employ in preparing the section of the bark, is to boil it for a 
few seconds in a very weak caustic solution, then to wash in abundance of water, and place the slice 
at once under the microscope, — the whole not occupying five minutes, — so that it is chemically 
impossible that any crystals (especially of quite soluble salts) could be formed under the circumstances. 
I call these crystals quite soluble (though far less soluble than the kinates I have mentioned), since 
they gradually dissolve, and in the course of a few weeks disappear in any menstruum that I know 
how to employ, — in this respect showing the difference of their nature from that of raphides or the 
granulations of inorganic salts in the crystal cells of the same bark, as also from the starch granules which 
are sometimes met with. 
I do not profess that my plan is so elaborate as theirs,- — it simply presents the natural appearances with 
less alteration ; and it was not till after long disappointment with preparations made in the manner 
ordinarily practised in England that I adopted the present more simple arrangement. 
Isolated Vessels. 
Whilst subjecting the very rich renewed bark of C. succirubra to microscopical examination, I met with 
a curious exemplification of the production of isolated reticulate vessels in a part of the plant where they 
have been rarely (if at all) observed in the same position, viz. in the bark itself. I had the opportunity of 
hearing a very interesting paper by Herbert Spencer, Esq., read before the Linnean Society, since pub- 
lished in the Transactions of this body in 1866, which enters into the question of the function of these 
spiral cells, and is accompanied by well-executed drawings resembling entirely those which I now present 
to the reader. The author reconsiders the question whether such vessels ought not to be looked upon as 
carriers of the plant juices, and adduces satisfactory evidence, as I think, to prove the affirmative of this 
proposition. Such vessels are found in leaves, and in the young and succulent parts of plants, also, as 
shown by Trecul, in some renewed tissues, but not ordinarily in the bark of trees. Their occurrence, as 
* f Journal de Pharmacie et de Chimie/ Avril 1868. 
H 
