100 BOTANICAL GAZETTE [FEBRUARY 
stolonifer, have been computed from four distinct series. In this 
way erratic results have been nullified, and the difference in effect, 
although not marked, may be regarded as constant. There is 
certainly a lessened attractive influence in the case of the decoction 
in which the fungi have grown; this might be due to the mere abstrac- 
tion from the decoction of nutrient substances, or to the conversion 
of compounds occurring in the decoction into compounds which are 
repellent in their effect, or to the secretion of products by the fungus 
which have a repellent effect. That the first is probably not the 
case is to be inferred from previous tests, in which these fungi have 
been found to grow as readily toward distilled water and other non- 
nutrients as toward nutrients; a mere decrease, therefore, in the 
amount of available nutriment could hardly have a pronounced 
effect. We must conclude, therefore, that a medium in which a 
fungus has grown may become less attractive, or more repellent, 
to the fungus through the agency of some undetermined substance 
or substances, which are secreted or otherwise formed by the growing 
fungus; this reaction would -be a special kind of negative chemo- 
tropism. 
Miss FERGUSON (13) found that germinating spores of Agaricus 
campestris, or bits of older growing mycelia, have a very marked 
effect in causing the germination of spores of this species; at the 
same time there seems to be a retarding effect upon the growth of 
the protruded germ-mycelium. Mycelium that is not growing, 
masses of ungerminated spores, or growing mycelia of other fungi 
do not have the same influence over germination. Her observations 
lead her to suppose that oxygen or carbon dioxid is not the deter- 
mining factor, but that some secretion is formed which stimulates 
or makes possible the emission of the germ-tubes. Other observa- 
tions relative to the influence of germinating spores upon the growth 
of fungi have been made by KrHLMAN (16) and REINHARDT (28); 
to these reference has already been made. : 
Numerous instances have been recorded of the influence by 
various plant cells upon the direction of movement and of growth 
of other cells of the same or a different kind, and the general terms 
cytotaxis and cytotropism have been applied to this peculiar sort 
of chemical influence. In the cases enumerated by PFEFFER (27, 
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