MICRO-ORGANISMS. 149 
plants were immersed in water, and allowed to rot spon 
taneously until the bast fibres ‘only remained. It is now 
proposed to infect the water with pure cultures of particular 
bacteria, and, by adding nutritive salts to favour their 
growth, the retting is accomplished in a few days in any 
class of water. The latter point is important, because the 
water of certain rivers, as the Lys, was considered a necessity 
for the process. The improvement not only saves the cost 
of transport of the crop to the river, but the flax is better 
than when the natural process is employed. Furthermore, 
by performing the retting, and drying in one closed vessel, 
the fibre is not so much broken. 
Starch, Indigo, and Tobacco. 
The preparation of starch, by fermenting potatoes, &c., 
with certain bacteria, has been attempted, but the process 
is too lengthy to compete with the ordinary one. 
. The fermentation of indigo was considered to be bacterio- 
logical, but we know now that it results from the activity 
of certain plant enzymes. One of these, a diastase, converts 
the indican into indigo-white, glucose, &c. The indigo- 
white is oxidised by an oxidising enzyme or oxidase in alka- 
line solution into indigo-blue. 
The curing of tobacco was also supposed to have been 
occasioned by the agency of bacteria, and even yet the sub- 
ject is under discussion ; but the evidence is in favour of the 
theory that it is brought about by the natural enzymes of 
the leaf. 
Many other fermentations of vegetable substances which 
at one time were considered as bacteriological are being 
shown to be caused by the enzymes inherent in the cells. of 
the plant. 
The Farming Industry. 
The changes that bacteria produce in _ nitrogenous 
material are of the greatest importance to the farming in- 
dustry, for they include (1) the conversion of manure of 
various kinds into suitable plant-food, (2) the losses accom- 
panying the change, and (3) the gain by the nitrogen- 
gatherers. In the first place, nitrogenous vegetable and 
animal matter of almost any description supply the nourish- 
ment necessary for the growth of most bacteria, so that in 
the presence of moisture a putrefactive fermentation quickly 
sets in. In the rotting of manure the straw, &c., rapidly 
loses its shape; the structure of the substances that went to 
make it, becomes altered and unrecognisable; and, at the 
