THE TOXICITY TO FUNGI OF VARIOUS OILS AND SALTS. 7 



hemp and cotton fibers, and starch grains, comes under the general 

 term "adsorption." It is often explained as a direct physical 

 affinity of the toxic chemical for the inert substance; that is, a con- 

 densation of the substance on the surface or in the interstices of the 

 insoluble matter, or the formation of a solid solution of the two, but 

 chemists and physicists are not at all in agreement in regard to these 

 explanations. 



Among others, True and Gies (29) and True and Oglevee (31) 

 worked upon this problem, using seedlings of Lupinus albus and a 

 number of inorganic and organic compounds. As adsorbing agents 

 such substances as sand, glass, filter paper, and paraffin were applied. 

 With copper sulphate they found that at least twice the usual toxic 

 concentration could be endured by the Lupinus roots when a suf- 

 ficient quantity of the insoluble matter was added to the hypertoxic 

 solution. In summarizing their work they remark: 



It appears in general that the presence of a considerable body of certain insoluble 

 substances in solutions of strongly toxic compounds both organic and inorganic in 

 their nature, be they electrolytes or not. tends to decrease the toxic activity of the 

 solutions in question. On the whole this ameliorating action is more clearly marked 

 in case the poisonous solutions concerned are dilute solutions of strong poisons than 

 when relatively concentrated solutions of weaker poisons are concerned. 



Fitch (8) conducted a series of experiments with sulphuric acid 

 and copper sulphate, using pottery, glass, sand, and filter paper as 

 the adsorbing agents and two common molds (Aspergillus niger and 

 Penicillium glaucum) as the test organisms. She established for fungi 

 the same phenomena of dilution that a number of other workers had 

 found to hold for flowering plants. 



The diversity of results secured when toxic substances are tested 

 on various media, particularly such as contain starch grains and 

 similar materials in suspension, no doubt is explained, in part at least, 

 on the basis of adsorption. 



RELATION OF TEMPERATURE TO FUNGOUS GROWTH AND TOXICITY. 



It is well known that temperature exerts a vital influence on the 

 growth and development of fungi. Not alone is the temperature 

 range which permits the growth of the organisms highly variable, 

 but also the optimum temperature in many cases varies for the differ- 

 ent species. Thus, for nine species of wood-destroying fungi studied, 

 Falck (5, 6) indicated a growth range lying between 3° and 44° C, 

 with the corresponding optima between 18° and 35° C. For Meru- 

 lius domesticus ( = M. laclirymans in part) this optimum falls between 

 18° and 22° C. 1 ; for Coniophora cerebella, 22° to 26° C; for Polyporus 

 vaporarius spumarius, 26° C; for Lenzites abietina, 29.5° C; for 



1 Hoffmann (13) states that under certain conditions of culture this optimum may be raised so as to 

 fall between 18° and 26° C 



