50 



extraordinarily poisonous to plants.^ Miani^ records the interesting 

 observation that in a vapor-saturated chamber the mere presence of 

 copper in the neighborhood of but not in contact with a hanging drop 

 of water containing spores of Ustilago and pollen grains of various 

 plants stimulated the germination of the latter. H. Schulz ^ found 

 that alcoholic fermentation is accelerated by the presence of a small 

 quantity of mercuric chloride and of other substances. The devel- 

 opment of Aspergillus and of Penicillium in glycerol cultures was 

 stimulated, according to Pfeffer/ b}^ the presence of small quantities 

 of zinc, manganese, cobalt, etc. Subsequently numerous experiments 

 as to chemical stimulation were made by Richards upon fungi. ^ 



1 For a classical discussion of the toxic effect of exceedingly dilute solutions of 

 metallic salts upon the alga Spirogyra,-see Nageli, Neue Denkschr. schweizerischen 

 Gesellsch. f. gesammt. Naturw., 33 (1893). Copper in a solution of 1 part to 

 1,000.000,000 of water was found to be fatal! (I.e., p. 23.) Attention has lately 

 been redirected to the extreme toxicity of copper by Deherain et Demoussy 

 [Comptes rendus, 132, 523 (1901)] and by H. Devaux (1. c, p. 717). The latter's 

 observation that protoplasm absorbs less copper when exposed during several 

 hours to a large quantity of a running very dilute solution (e. g., of 1 part copper 

 to 400,000,000 parts water) than when placed for a short time in a single drop of a 

 much more concentrated solution ( 1 part copper to 30,000 parts water) leaves wholly 

 unexplained the negative results as to the extraordinary toxicity of this substance 

 recorded by Miani [Ber. deutsch. bot. Gesellsch.. 19, 461 (1901)], who immersed 

 his subjects for a long period in a single drop of solution. Nageli's experiments 

 have been more recently repeated (upon Spirogyra and other organisms) by Israel 

 und Kiingmann [Virchow's Archiv, 147, 293 (1897)], who made careful studies of 

 the "oligodynamic "' effects produced by extremely dilute solutions of copper. A 

 noteworthy contribution to this subject by Galeotti has lately appeared [Biol. 

 Centralbl., 21, 321 (1901)], in which the effect produced by a '• colloidal"' solution 

 of copper [prepared after the electrical method recently described by Bredig and 

 Miiller in Zeitschr. fiir physik. Chemie, 31, 258 (1899)] is compared with that of an 

 "ionic"' solution of copper sulphate containing an equivalent amount of copper. 

 This author found that the former (colloidal) solution plasmolyzed the protoplasm 

 of Spirogyra in a dilution (1 gram-atom copper in 12,600,000 to 126,000,000 liters of 

 water) at which the ionic solution (of copper sulphate) produced no effect what- 

 ever. He therefore concludes that the action of the colloidal solution is a catalytic 

 one, closely analogous to the catalyzing action of such colloidal solutions (of cop- 

 per and other metals) upon hydrogen superoxide. 



•^Ber. deutsch. bot. Gesellsch., 19, 461 (1901). 



•'Pfiuger"s Archiv f , die gesammte Physiol.. 42, 517 (1888). 



^ Jahrb. fiir wiss. Botanik, 28, 238 (1895). 



^Ibid.. 30, 665 (1897). Richards experimented with sulphate of iron and with 

 salts of zinc, cobalt, nickel, and manganese, as well as other substances, using as 

 subjects one species each of Aspergillus, Botrytis, and Penicillium. The estimation 

 of the amount of stimulus obtained was based upon the increase in dry weight of 

 the whole mass of mycelium in the culture as compared with that in a control free 

 from the stimulating substance. Zinc sulphate was found to be the most power- 

 ful stimulant, while important results were also obtained with sulphates of iron, 

 cobalt, and nickel. Salts of lithium were likewise very effective. It was found, 

 however, that acceleration of the development of the mycelium was accompanied 

 by an unfavorable influence upon the production of conidia, when salts of zinc or 

 of iron, amygdaline, or morphine were added to the culture solution. In other 

 words, a stimulation of one function or phase of development doec not neces- 

 sarily imply stimulation of the organism as to all its functions. 



