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TRANSACTIONS OF SECTION B. 693 
‘Budding’ and ‘grafting’ are processes involving the establishment of a 
*ymbiosis. 
The nodules on the roots of leguminous plants. Discovery and controversy as 
to their nature. They contain living bacteroids, which penetrate the root hairs 
and flourish in the living cells. Universality of these nodules on healthy roots, 
Hellriegel and Willfarth’s cultures, and evidence as to the fixation of nitrogen. 
Laurent and Schloesing’s proof that nitrogen is fixed from the air. 
The leguminous nodules a case of symbiosis, comparable to galls. 
Other instances not yet explained. Nodules on the roots of Juncus, Myrica, 
and other plants. 
Symbiotic fermentations. All natural fermentations mixed. Pure cultures 
.and the importance of synthetic cultures. 
Kephir, the ginger-beer plant, and other instances of symbiotic ferments. 
Decomposition of cellulose. Nitrifying and denitrifying organisms. The direct 
alcoholic fermentation of starch by the simultaneous action of two fungi. 
Return to the idea of symbiosis. Necessity of limiting the term. Antibiosis 
(antagonism). Metabiosis. Difficulty of distinguishing in given cases. Hypo- 
thetical considerations, and importance of further investigations. 
Particular Cases. 
The above may be accepted as affording general headings under which the 
‘subject of symbiosis might be treated. 
For the purposes of this discussion, I proceed to consider some special cases, 
and limit myself—as requested to do—to certain aspects of symbiotic fermen- 
tations. 
Several cases of symbiosis among bacteria are now known. Apart from 
numerous instances of temporary association between pathogenic micro-organisms 
and animals such as earth-worms, rats, flies, ticks, and mosquitoes, and which 
disseminate their germs and infect cattle, sheep, horses, and men, reminding us of 
the transference of the spores ot Botrytis by bees, which carry this parasite with 
the pollen and infect the stigmas of bilberries with the parasite ; or which act the 
part of intermediate hosts to the disease germs, much as certain pond snails do 
to the liver-fluke of sheep, we now know several cases of symbiosis between 
two species of bacteria or of fungi, or between a bacterium and a fungus, each 
symbiont being incapable of carrying on alone the work which the symbiotic 
association is able to perform—a point which is essential to the definition of 
symbiosis in the narrower sense, z.e. the co-operation of two associated organs to 
their mutual advantage. 
A striking example is afforded by certain bacteria concerned in the destruction 
of cellulose in ponds, bogs, rivers, &c. Van Senus found that a certain anaérobic 
bacterium, resembling, if not identical with, Van Tieghem’s b. Amylobacter, 
though incapable of dissolving cellulose by itself, can do so if associated with 
another bacterium, also incapable of itself attacking cellulose. 2B. Amylobacter 
can ferment pectose compounds, and is thus capable of isolating cells one from 
another, but cellulose is not attacked by it. 
Van Senus believed that the one bacillus destroys certain products of fermen- 
tation excreted by B. Amylobacter, which inhibit its cellulose-fermenting powers. 
I may remark here, that if a sound potato, rhizome, or other underground 
organ is placed in water and the air exhausted as completely as possible, I almost 
invariably find its cellulose walls destroyed in a few days by a mixture cf bacteria, 
and with the symptoms found in many kinds of ‘wet rot.’ There is no reason to 
believe that these organs would rot if merely wet and not deprived of air, since 
they lie in ordinary soil—even moist soil—for weeks or months, with plenty of 
water in their tissues, and respire oxygen, as is well known. The presumption 
is that the anaérobic conditions set up in the experiment described favour certain 
forms of soil bacteria, such as Van Senus worked with, and enable them to co- 
operate in the destruction of the cell walls. 
An even more remarkable example is given by Winogradsky, who found that 
the anaérobic bacterium known as Clostridium Pasteurianum is able, if supplied 
