THE GINGER BEER PLANT. 279 
rendered palatable with various essences, and impregnated with 
carbonic acid gas by means of machinery. The former is generally 
called in Lancashire “stqne-pop,” while the latter is produced by 
the manufacturer of aerated waters. 
It was with some degree of surprise that I heard of a specific 
ginger-beer plant, having always been under the impression that 
the substance inducing the fermentative change was ordinary yeast 
or barm, but on making inquiries into the matter I found the same 
“plant” in many localities producing a beverage drunk in the sum- 
mer as ginger-beer. 
The modus operandi appears to be as follows :—A solution of 
sugar and water is placed in a large mug or jar, standing in a warm 
corner of the kitchen ; the ginger-beer plant is added, gently stirred, 
and fermentation allowed to go on without any more attention. 
In a few days a large quantity of free carbonic acid is found in 
solution, and very small quantities of alcohol also; the “plant” 
remaining at the bottom, and the liquor above it being remarkably 
clear. This liquid is baled off for use, and when the quantity is 
getting low, the jar is filled up again with a solution of sugar and 
water, to undergo the same process as before. It is not quite clear 
to me yet how the increase of the plant is brought about in a solu- 
tion of refined sugar ; but it has been increasing with me, although 
fed with a pure sugar. One can scarcely believe that this multi- 
plication can go on indefinitely without fresh increment of nitrogen- 
ous matter, phosphate. Query,—is the absorption of atmospheric 
ammonia by the liquid, sufficient for this ? 
We now come to the most important part of the paper: What is 
the ginger-beer plant? All of you have doubtless heard of, and 
many may have seen, the yeast plant, which induces the alcoholic 
fermentation in sugar. It should be known that there are two dis- 
tinct varieties of commercial yeast: ordinary yeast, or that which 
collects on the surface of beer in the usual method of brewing, and 
sedimentary yeast, which falls to the bottom of the fermenting 
vessel during the brewing of Lager beer. The first is active at tem- 
peratures varying from 15° to 20° C., while sedimentary yeast is 
active at temperatures from 6° to 8° C. I suppose we may take it 
for granted that the first batch of yeast formed in the world as a 
commercial operation, must have arisen spontaneously, and that 
some process of differentiation has arisen, tending to separate the 
ordinary from the sedimentary. The differences between these 
two forms will be seen from fig. 68, the surface yeast on the right, 
the sedimentary on the left. 
A glance at our ginger-beer plant will soon show us that it has 
but little in common with the ordinary or surface yeast. ‘The fer- 
menting solution is quite clear, even to the very top, and the 
appearance of the plant, taken by itself, is far different to that of 
