June 14, 1S73.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
991 
The play of colour when the prisms are crossed with¬ 
out the intervention of a selenite filter is very fine. 
The cells of the parenchyma are thin-walled, sub- 
globose in shape, and contain, besides the crystal 
prisms and the ordinary albuminous contents, tannic 
acid and a saccharine substance that very rapidly 
reduces Fehling’s test. The tannin is most largely 
present in the middle portion of the bark, in the 
medullary rays, and in the oil receptacula distributed 
through the bark, and in small quantities only in the 
sub-epidermic receptacula. The crystals are not im¬ 
bedded in the cell-contents, and are evidently an 
oxalate of lime, and perhaps, some of them, of some 
other salt. Starch very doubtfully present in any 
of the specimens I have examined. 
The medullary rays are narrow, and composed of 
nearly square cells containing a yellow, red-brown 
substance consisting of tannin, an oil, and protein 
substance. The cell walls at right angles to the di¬ 
rection of the rays are much more delicate than the 
other walls, and easily give way under tension, much 
facilitating the “ stripping ” of the bark. 
Two forms of oil and resin vessels are common in 
the inner portion of the bark. One very long and 
thin-walled kind lies alongside the liber-tubes, and 
is not to be distinguished from them until the sec¬ 
tion has been deprived of all its colouring-matter and 
is either slightly stained or is examined by polarized 
light. The other form consists of irregularly-shaped 
cells, thick-walled and consolidated, and very mi¬ 
nutely porous, of very various shapes, and chiefly 
aggregated in the middle portion of the bark. . These 
■cells can only be studied after the careful application 
of ether and alcohol to remove resin, and sulphuric 
acid and chlorate of potash to remove albuminous 
and gummy matters and to bleach the specimen. 
Large receptacula in the form of intercellular spaces, 
bounded by small cells and very similar to those 
found in the rind of the orange, occur near the exte¬ 
rior, and also, but rarely, in the inner portions of the 
bark, and are easily seen if the section containing 
them be partially exhausted with alcohol and then 
stained with iodine solution. The contents of these 
receptacula apparently do not include tannic acid, 
at any rate not in a state sufficiently free to give the 
usual reaction with iron salts. (A section. stained 
with proto-sulphate of iron is very interesting, and 
shows the distribution of the astringent principle 
very clearly.) 
To conclude, it is doubtful whether any bark re¬ 
quires more careful examination, or is worthy of more 
careful study, than the one that has occupied us so 
long. The leaves may now perhaps be noticed, as 
the substances present in them bear some relation to 
the oils and resins in the bark. As has already been 
said, the leaves are more or less sabre-shaped, and 
bear a white bloom, due to depauperation of the epi¬ 
dermis, here as in all the Australian Myrtaceoe of 
abnormal development. The longer leaves have great 
numbers of semi-lunar stomates on each surface, and 
the two surfaces agree more closely than is usually 
the case. This might be expected, from the fact that 
these leaves grow edgeways, and not, as our English 
and most other leaves, with their flat sides to the sky 
and sun. The structure of the petiole should first 
-en^ao'e our attention on commencing the histology of 
the leaf. The first thing that we notice on examin¬ 
ing a transverse section is the presence of receptacula 
a Tittle within the epidermis, not immediately be¬ 
neath it, as in the bark and in the rind of orange, 
containing a yellow essential oil, similar to the oil 
of the bark but lighter in colour, probably from the 
absence of one of the tannic compounds, to which 
a portion of the darker colour of the bark oil is due. 
These receptacula are precisely similar in construc¬ 
tion to the other one, and do not on this account re¬ 
quire further notice here. 
The cells of the epidermis are thickened, not 
so compressed as usual, and much longer than broad 
(differing, however, much in this respect in different 
specimens). The subepidermal layer is chiefly 
composed of globose cells, many of which contain a 
rose or rose-purple chromule,* often present in suffix 
cient quantity to give a decided purple colour to the 
petiole and midrib. The parenchyma cells are much 
tliicker-walled than in the bark, and contain chloro¬ 
phyll, and a few starch granules. Crystals are not 
usually abundant. The central woody tissue is by 
no means in the circular bundle commonly found in 
the petioles of the leaves of ligneous plants, but 
resembles a section through an involute vernation, 
the opening of the “scroll” is occupied by wood 
cells nearly filled with ligneous deposits, and the 
small central cavity containing only protein matter. 
Within the scroll are ordinary parenchyma cells con¬ 
taining granular substances, starch and small crystals. 
The liber-cells bounding the “ scroll” are larger than 
the inner and have larger central cavities. Their 
resemblance to the cord-like liber-cells of the bark 
is very close, and their contents are very similar. 
The structure of the “ scroll” itself is somewhat 
complex and consists chiefly of wood fibres, pitted 
and dotted, fibrous and annular vessels, all interest¬ 
ing, but requiring more space than can be devoted to 
them here. # 
The leaves are easily sectionized if they be placed in 
a soft split cork, and the usual section-cutting instru¬ 
ment be made use of. The epidermis is composed of 
irregular cells, little compressed and nearly equally 
thickened on each cell wall. The stomates are very 
numerous, and consist of two equally-sized semilunar 
cells, the whole stomate being of course circular, the 
semilunar cells containing no chlorophyll, but an 
amorphous semigranular substance, of which I have 
not been able to ascertain the nature. Exudations 
of a yellow resinoid substance, an oxidation product 
probably of one of the oils of the leaf, is found on the 
surface of the older leaves, as tear-shaped masses im¬ 
mediately above pear-shaped receptacula situate below 
the epidermal and subepidermal layers. The recepta¬ 
cula within the leaf are of two forms, one circular m 
cross-sections, and not communicating with the ex¬ 
terior, the other pear-shaped, and frequently opening 
at the surface by a small circular orifice, not due 
merely to disruption of the outer cell wall, but 
often perfectly formed as a pseudo-stomate. lhe 
contents of the two receptacula are slightly different, 
the latter containing the more camphoraceous oil, 
not, however, unlikely an oxidation product of the 
other. The middle layers of the leaf do not require 
special notice. The margin, where the submargma 
vein characteristic of Myrtaceoe is found, requires 
brief notice only in one particular. Within the 
wood cells, of which the hard margin is chiefly com - 
posed, lie small aggregations of porous cells, appa¬ 
rently connected with, or the terminals of, the vessels, 
with little or no contents and performing no appa- 
* A product, as we shall see presently, of one of the 
chlorophylls or chlorophyll compounds of the leaves. 
