550 Ward. — Symbiosis. 
swollen and modified owing to the presence of Fungi, which 
do not injure the plant, but link its roots to the decomposing 
leaves around. Explanation as an instance of symbiosis. 
Evidence partly anatomical and partly experimental (8). 
‘ Budding ’ and ‘ grafting 5 are processes involving the 
establishment of a symbiosis. 
The nodules on the roots of leguminous plants (9). Dis- 
covery 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 (10). Laurent and Schloesing’s proof 
that nitrogen is fixed from the air (11). 
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 (12). 
Symbiotic fermentations (13). All natural fermentations 
mixed. Pure cultures and the importance of synthetic 
cultures. 
Kephir (14), the ginger-beer plant, and other instances of 
symbiotic ferments (15). Decomposition of cellulose (16). 
Nitrifying and de-nitrifying organisms (17). The direct 
alcoholic fermentation of starch by the simultaneous action 
of two Fungi (18). 
Return to the idea of symbiosis. Necessity of limiting 
the term. Antibiosis (19) (antagonism). Metabiosis (20). 
Difficulty of distinguishing in given cases. Hypothetical 
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 fermentations. 
