600 
THE TROPICAL AGEICULTURIST. [March 1, 1899. 
with minute papillae, to be mentioned later under 
niicroscopical considerations. 
The external surface of the fruit is the epicarp, 
which is composed of Lluck-walled refrular cells, 
disposed in a single row. lieiieath this the tis-^aes 
are very thin walled and lax, containing con- 
sideralile amounts of an oily substance with the 
characteristic otlor ot vanillin, and also containing 
a large number of line acicular crystals of calcium 
oxalate. These are in general larger than the 
crystals found on the exterior of the fruit. The 
polygonal cells of the mesocarp are finely pitted 
in the main, but a number of them, es|)ecially 
near the ])eripheiy, are irregularly marked. 
In the niesopliyll are the libro-vascular bundles. 
The.se are irregularly scattered, the txternal ones 
being somewhat ladially disposeil, while those 
further in are not infrequently tangentially 
arranged. The bundles are lose and lax, and 
are built on the cmicuntrie type. In thecentie 
of the bundle the fibres and sieve-tubes are found. 
These are surroande I by a number of du:;ts, 
which are usually spiral in type, and sometimes 
interspersed with annular ducts. Irregular resi- 
nous masses and ju'lsms of vanillin may be found 
in the tissues of the niesopliyll. 
The innermost layer of the mesocar]) is made 
of smooth, slightly flattened cells, which bear a 
single row ot unicellular papillose hairs, which 
project into the central cavity. These hairs have 
the interesting function of secreting the oily and 
resinous substances which elaborate vanillin. 
A few words upon the microscopical identilication 
of false crystalline structures on the outside of 
the fruit. Unscrupulous dealers often use benzoic 
acid to make a false appearance of vanillin. It 
is to be di."itinguished from the real article by 
the fact that its crystals ore (lattened and rhom- 
boidal, whereas the crystalls of vanillin are 
usually acicular and stand out, as a rule, at 
right angles to the surface of the fruit, 
THE MOULDS UPON THE FRUIT. 
A beautiful suecimen of the fruits was given 
to me by Mr. Henning which showed a marked 
development of mould oiv the inside. Fragments 
of this mouldy fruit were planted upon gelatin 
and nutrient agar-agar with the following results : 
The principal mould found was "Aspergillus re- 
pens;" another form was the " Mucor circinel- 
loides." The hrst of these moulds is extremely 
common over the civilized world. The second is 
a form that has been found by me in the air of 
this city, but it is extremely rare. In Europe 
it is reported much more frequently. The characters 
of these moulds can be seen by consulting the 
Journal of Pliarinacoloyy for November, 1897. 
A number of bacteria were also obtained, but 
these were in all probability from the air, and 
not deserving of special mention. 
THE CHEMISTRY OP VANILLIN. 
By Virgil Coblentz Ph. d. 
The odorous properties of the vanilla bean 
reside in the crystalline principle vanillin and a 
minute quantity of a balsam-like substance which 
is found in the seed. As is well known, the 
odorous principles are not well developed until 
during the curing process. It is then evident 
that there pre-exists in this fruit a complex 
organic body, which undergoes hydrolysis, or 
oxidation, during the sweating process, the exact 
nature of which changes has never been studied. 
METHODS OF PREPARING RUBBER. 
By R. H. BiFrEN. 
.So much lias been written within the last few 
years on the subject of Irdiaiubber, the f-ouices 
of our supjdy, and the pos-sibility of acclimati- 
zing tlie bcHt-^ielding iiees in our colonies, thot 
at first sight it may appear tiiat there is little 
more to be swid. A study of the methods in 
use for preparing rubber Irom the latex, or milk, 
niay however be of use to many inlfrt-sted in 
the formation of plantations, especially if some 
attention is jmid at the same lime to tiie in- 
accurate statements made in some lecent publi- 
cations, which apiiarently have disregarded the 
valuable series of papers on the mbjeci con- 
tained in our one journal devoted to economic 
botany, the " Kew Bulletin. ' 
The methods in use at present are either the 
out come of the limiieil exjierience of uncivilised 
peoples, or the application of experiments made 
without (laying due attention to what is known 
of the chemical constitution and physical |iro)i<-rtie<i 
of latex. As a good example of ilie latter we 
may take the experimenis of Morisse,' who found 
that coagulation was brought about in the latex of 
Ueiea by the addition of alcohol, plieno, hydioch- 
loric acid, nitric acid, sulphuric acid, calcium 
chloride, ferric chloride, corrosive sublimate, &c. 
As the outcome ol these experiments, a mixture 
of phenolin alcoholic solution, and dilute sulphuric 
acid, was recommended as a coagulating af.ent. 
The latex is, as a general rule, a thick, white 
fluid, composed of small particles of nibber in 
suspen.sion in a clear watery solution of various 
substances. Unfortunately, only the latex of a 
few trees has, as yet, been chemically examined 
when fresh. 
The analysis of the latex of Hevca brasiliensii 
shows that it contains : — 
Rubber 32 per cent. 
Proteid matter 2 .i ,, 
Calcium and sodium salts 9 7 „ 
Kesin traces 
Water 55 to 56 „ 
It is slightly alkaline to litmus paper.f 
The presence of albumin, globulin, and other 
proteids, has been demonstrated by Green J in 
some other rubber-yielding latices; 
Asa general rule all these substances are to 
be fouiid in rubber as it is at oresent prepared, 
often witii others added to bring about coagulation 
of thelatex,and accidentally or intentionally added 
impurities such as bark and clay. In all cases 
the percentage of impurities is la'-ge, how large 
we shall see later, and when it is remembered 
that some cause a rapid deterioration of the r.ibber, 
it is obviously much to the interest of those 
connected with the industry that a niethgd of 
preparation should be adopted which would 
minimize them or ensure their absence. 
I propose now to consider a few of the better- 
known varieties of rubber. 
Fard Riibber is the product of Havea brasiliensis, 
a tree which thrives in many parts of the Amazon 
valley, British Guiana, &c. As pointed out by 
Churchill§ in his consular report, there is no 
danger of this source of supplying beconiin<r ex- 
hausted, though this is the frequent cry of com- 
* Seeligman, Lamy, et Falconnet ; " L/e Caoitchouo 
eta Guttapercha.'" Paris, 1896. p. C8. 
f ''Le Caoutchouc," (fee, p. 94. 
i Green, "Proc- Roy. Soc," 1886, p. 2i. 
§ " Kew Bulletin," 1898, p. 241. 
