i 54 [June, 1902.] 
IMPERIAL INSTITUTE JOURNAL. Vol. VIII. No. 90. 
of moisture instead of the 14 to rS per cent, usually present in the latter, so that its uniform 
distribution can easily be effected. Its average composition is 
shown by the following 
analysis : — 
Moisture (lost at ioo° C.) 
4-15 
Combined water and loss on ignition 
12*86 
^Phosphoric acid (total) 
13-60 
Lime ........ 
35 * r 5 
Sulphuric acid ...... 
28-50 
Oxides of iron, alumina, magnesia, etc. 
2'34 
Insoluble siliceous matter .... 
3 '40 
100-00 
*Equal to phosphate of lime 
29*68 
The manure, therefore, furnishes fully io per cent, more lime than ordinary super- 
phosphate, and its superiority over basic slag in point of solubility is illustrated by the 
following figures : — 
Solubility in Cold Water after 48 hours. 1 part 
Manure to 1,000 parts Water. 
Solubility in Citric Acid Solution (1 in i,ood) after 
24 hours. 1 part Manure to 1,000 parts Solution. 
Basic 
Super- 
phosph. 
Basic 
Slag. 
Percentage dissolved 
66 "So 
6‘6o 
Containing : — 
Lime 
Phosphoric Acid . 
22-28 
none 
4*70 
none 
Basic 
Super- 
phosph. 
Basig 
Slag. 
Percentage dissolved 
94*20 
38*80 
Containing : — 
Lime . 
3473 
22*17 
Phosphoric acid 
12*45 
8*70 
Equal to phosphate 
27*18 
iS *99 
of lime 
The basic superphosphate is, therefore, ten times more soluble in water than a good finely- 
ground basic slag, and if the figures for the solubility in a weak solution of citric acid 
be compared, as representing more nearly the amount of available plant food in the two cases, 
it will be seen to be much superior. It is much more soluble, yields more lime and phosphoric 
acid to the solvent, and, further, out of a total content of phosphate equal to 29 ’68 per cent, of 
phosphate of lime, an amount equal to 27-18 per cent, was dissolved. The sample of basic 
slag used contained 38*97 per cent, of phosphate of lime, and of this an amount equal to 
1 8 -99 per cent., or less than half, was dissolved. The basic superphosphate must, therefore, 
be regarded as superior in fertilizing power to ordinary basic slag, and is specially recom- 
mended as a quick-acting phosphatic manure suitable as a spring dressing for crops grown 
upon soil containing less than I per cent, of lime. It will not take the place of ordinary 
superphosphate upon soils containing plenty of lime, or that of well-ground slag on damp, 
sour land, but on the above-mentioned soils, which represent a large area of the cultivated 
land in the United Kingdom, it should prove a useful and valuable fertilizer. During last 
season, 1901, the new manure was tried in many parts of the country, and the results of 
these practical tests have fully confirmed the favourable opinion founded on the laboratory 
experiments. 
CULTIVATION OF VANILLA IN GERMAN EAST AFRICA. 
The current number of DerTropenpflanzer (April, 1902), the organ of the German Colonial 
Economic Committee, contains an interesting article on this subject by Herr Blitzner, a planter 
who has grown vanilla in Africa, and who has had considerable experience in the prepara- 
tion of this material for the European market. The object of the article is to extend the 
cultivation of vanilla in such German colonies as the Cameroons and Togoland, and for this 
purpose full information on the question of choosing suitable localities for the plantations, 
the artificial ripening of the pods in inclement weather, and the proper packing of the 
commodity for export to Europe are given, and may be commended to English planters in 
tropical colonies where vanilla cultivation is possible. 
Of the various species of plants yielding vanilla the one giving the best results is Vanilla 
planifolia , which begins to bear usually in the third year after planting and yields from 3 to 5 
crops. It flowers in East Africa from August to November and bears fruit from April to 
July, the latter requiring about eight months to ripen in normal weather, and a further two 
months for drying and fermentation. For a plantation of about 10,000 plants, 15 labourers 
are necessary, and the wages of the latter on the East Coast of Africa are about 3§d. per 
day each. In forming a vanilla garden special attention should be paid to the selection of a 
site protected from wind, shaded by trees from the direct heat of the sun, and in the 
neighbourhood of a stream which is not dried up in the hot weather. The importance of the 
latter is obvious when it is remembered that the roots of the plant only penetrate about 
twelve inches into the ground and, therefore, obtain water only from the easily dried surface soil. 
For this reason it is necessary to have a good supply of water fof irrigation in dry weather. 
The plants are arranged in parallel rows about five feet apart, passages being left at intervals of 
about 45 to 50 yards to permit of regular inspection of the plants. As supports for the 
orchids poles of ebony are sufficient in situations where there is sufficient natural shade, but, 
if the latter is deficient, then Jatropha curcao may be grown in the garden to afford both 
shade and support. It is usually best to place the young vanilla plants for about a fortnight 
in a well-shaded moist situation where they are kept well watered, and then to transplant 
them to the small pits about twelve inches deep already prepared with leaf mould for their 
reception in the plantation, the aerial portion of the plant being at once secured to the 
support by bast or banana fibre. The orchids should not be allowed to grow higher than 
about 5 feet, and when they reach this stage the heads should be carefully bent towards the 
ground. The plants require manuring with leaf mould or similar material once a year. 
The chief enemies of the vanilla orchid are beetles, snails and caterpillars, which eat the 
fleshy roots and young stems, the only remedy being the constant examination of the plants, 
and destruction of these insects, when they are found. The flowering period is an important 
time, since the plant, outside its native habitat, is not self-fertilising, and must therefore be 
pollinated individually by hand. This work, although rather a delicate operation, can be 
readily taught to negroes. In order to secure pods of good quality it is necessary to limit 
the fruit production of each plant to from 20 to 25, although in special cases the maximum 
limit may be 35 ; if this number be exceeded the ripe fruits suffer in size, appearance and 
flavour. Ripeness of the fruits is indicated by the formation of a yellowish patch at the 
base, and at this point they should be gathered by breaking the attachment to the stem 
cautiously with the finger nail. 
The operation of curing the ripe pods has an important bearing on the quality of the 
vanilla ultimately obtained, and great care has to be exercised in the carrying out of the 
drying and fermenting processes. The pods, after gathering, are sorted on the following day 
into about three sizes, and placed in large pots warmed to about So 0 C by hot water for 
about 14 seconds, then packed in wool-lined boxes for a day, and finally dried with a linen 
cloth and placed in the sun on wool-lined trays for complete desiccation. In wet weather 
the exposure to the sun is dispensed with and the final drying accomplished by careful 
heating in ovens kept at temperatures between So 0 and ioo° C. The prepared pods are then 
stored in drying rooms and finally in large metal-lined boxes. 
The preparation of the finished vanilla for the market, consists in sorting it into various 
qualities according to its appearance, size of pods and flavour. The pods of the same 
quality are then tied into bundles of about 50 to 60 each, secured with fine twine and packed 
into well-closed zinc- or parchment-lined boxes, capable of holding from 10 to 12 lb. of the 
product. 
THE FERMENT OF THE TEA LEAF. 
Although the change of the moist green tea leaf into the dried leaf with a coppery reddish 
black colour is one of the most important operations in the manufacture of black tea, and 
requiring the greatest care ; yet the causes bringing about and influencing this change are not 
known with any certainty. Almost the only investigations made, until recently, were by 
Mr. Bamber, who, by several experiments, showed fairly conclusively that in some way or other 
the change was a matter of oxidation ; for instance, no alteration was observed in the green 
leaves when they were kept in an atmosphere of carbon dioxide or in a vacuum, and the 
action of pure oxygen was found to be more rapid than that of air, although the resulting 
infusion was the same as that from the leaves exposed to air. It was also shown that bacteria 
or living organisms could have no agency in the change, because the leaves could be fermented 
equally well at 73 0 Fahr. (the usual temperature) as at 120° Fahr., at which temperature all 
germs would be destroyed. Solutions of such oxidising agents as potassium permanganate 
and hydrogen peroxide were tried on the leaves ; but no appreciable effect could be noticed, 
the change proceeding in a perfectly normal manner. These results have recently been con- 
firmed by other investigators, who have also attempted to isolate a ferment or enzyme from 
the leaves with varying success. 
A report detailing the experiments made by Mr. Harold H. Mann appeared in the 
January and February issues of the Tropical Agriculturist , from which it would seem that he 
has isolated an oxidising ferment or “ oxydase,” accounting not only for the change in the 
nature of the leaf, but also for the character of the tea produced. The enzyme was prepared 
by digesting with cold water, for two hours, a thoroughly powdered mixture of tea leaves with 
half their weight of hide powder, which has the property of absorbing all tannin matters from 
the aqueous extracts ; the clear filtered extract was then poured into alcohol, and the enzyme, 
which was precipitated as a white slimy mass, removed and re-dissolved in water. The esti- 
mation of the enzyme in water could be done coIourimetricaUy by the production of a blue 
colour on the addition of a few drops of tincture of “guaiacum resin,” the depth of colour 
indicating the proportion of enzyme present. The oxidising nature of the ferment was readily 
shown ; thus, solutions of pyrogallic acid and of hydroquinone were rapidly oxidised in 
presence of the enzyme. It was found that all action of the ferment was stopped by heating to 
1 30° Fahr., and further heating to 170° Fahr. was sufficient to kill the ferment in a few minutes ; 
a o‘i per cent, solution of sulphuric acid or a 3 per cent, solution of acetic acid or alkali • 
was equally destructive ; but, curiously, a faintly acid solution has an invigorating effect on the 
ferment. The proportion of enzymes in the different parts of the tea shoot have been exam- 
ined, and it appears that the greatest amount is in the stalk and the unopened tip leaf ; 
but as the unopened tip leaf contains nearly double the amount of acid, tannin and 
phosphoric acid that there is in the stalk, it is reasoned that the best tea 
results from a large amount of enzyme combined with the largest acidity and 
percentage of tannin. This theory is supported by the results of analysis of different 
grades of tea, it appearing that the flavour and general quality of the tea is directly 
proportional to the amount of enzyme in the leaf ; it is noticed also that the percentage of 
phosphoric acid is greatest in the best grades. Mr. Mann reports the discovery that the 
effect of “ withering” is to increase the amount of enzyme present by sometimes as much as 
Soper cent. ; also, together with the “ oxydase” or active oxidising ferment, he finds a small 
quantity of enzyme generally present, which seems to take no part in the process. 
One or two other investigators have recently reported the isolation of minute quantities 
of an oxidising ferment, but which they have not yet examined. 
LUMINOUS BACTERIA. 
Several species of bacteria have been found to possess the power of emitting light under 
certain conditions and, as the phenomenon presents many points of interest, the results of a 
recent investigation by Dr. J. E. Barnard {Nature, Vol. 65, p. 536) may be briefly recorded. 
The number of such species hitherto isolated is about twenty-five, but it is extremely probable 
that some of thase are identical or, at any rate, very closely allied. They occur principally, if 
not exclusively, in sea water, and, although it is considered improbable that they produce any 
general luminosity of the sea, this may occasionally happen in the tropics where the conditions 
are most favourable. One organism in particular, the Photobacterium Indicum, forms a 
surface pellicle in artificial fluid cultures, which is very luminous, and this may at times be 
the cause of luminosity on the surface of the sea. The emission of light by a unicellular 
organism such as a bacterium is, in itself, remarkable, since there is no evidence of any special 
structure in the cell, and there is the further point that it is apparently, unaccompanied by 
any evolution of heat. The production of light, like that of heat in other organisms, must be 
attributed to the vital activity of the cell, being always accompanied by absorption of oxygen 
and evolution of carbon dioxide, but at present no explanation can be given of the fact that 
in these cases all the liberated energy appears as light. 
In all marine light-producing animals the phenomenon is intermittent, being brought 
about by some external stimulus, and this may be so in the case of the bacteria, but, as the 
individual organism is not sufficiently luminous to be studied under the microscope by its 
own light, it is difficult to decide the point. A supply of free oxygen appears to be essential 
for continued luminosity, and in fluid media, where the oxygen in solution is quickly used up, 
means must be taken to replenish it, either by leading in a stream of the gas, when very 
brilliant effects are produced, or by frequent agitation. Agitation alone does not seem to be 
a direct exciting cause of luminosity, only serving to introduce fresh oxygen, and if the 
bacteria are kept perfectly at rest they will emit light as long as a continuous supply of 
oxygen is maintained. 
Artificial cultures of the bacteria are best made on a medium containing a considerable 
percentage of a soluble chloride in addition to the usual nutritive material, for although they 
can be grown on ordinary media, all of them will not then emit light and none of them will 
produce their maximum effect. Any of the chlorides present in sea-water will increase the 
luminosity if added in suitable proportions, but the best results are obtained by adding to the 
culture medium 2 '6 per cent, of sodium chloride, *075 per cent, of magnesium chloride and 
'3 per cent, of potassium chloride. The temperature at which the different luminous bacteria 
will grow varies considerably. Those found in northern latitudes will reproduce themselves 
and remain luminous at o° C., but their optimum temperature, at which reproduction is very 
rapid and the emission of light is at its maximum, is about 15 0 C. ; those from the tropics, on 
the other hand, will grow at much higher temperatures, but in no case is the optimum as high 
as blood-heat, 37 0 C. The light emitted by these bacteria was found to give a continuous 
spectrum which visually only includes the green and blue, the brightest portion lying between 
the lines F. and G., but photographs show a slight extension towards the violet. The 
cultures can be photographed entirely by their own light, they retain their light-giving power 
for long periods, and the luminosity is always greatest at those points where reproduction is 
taking place. 
