51 



Recently au important paper upon the effect of certain chemical 

 stimuli upon fungi and alga? has been published b}^ Ono.^ 



Similar results as to the stimulation of life processes afforded by the 

 presence of small quantities of various non-nutritive substances have 

 been obtained in experiments with animals. Loeb ^ found this to be 

 true of certain acids, hj^drates, and mineral salts, the accelerating 

 effect produced by the solutions upon the absorption of water by 

 muscles, the rhythmical contraction of muscles and the segmentation 

 of eggs being attributed to hydrogen ions, hydroxyl ions, or different 

 basic cathions, as the case may be.^ 



The as yet obscure pi-oblem of the mode of action of chemical 

 stimuli as regards plants has been discussed by Pfeffer,^ from whom 

 it may be permissible to quote at some length : 



"In the regulation of activity chemical stimuli certainl}^ play a 

 very extensive part. It is obviously a matter of chemical stimula- 

 tion that the seeds of Orobanclie and of Lathr^ea germinate only 

 upon the roots of host plants, and probably the same occurs with 

 fungi. In the case of initiatory or only regulatory stimuli, there may 

 be partly involved substances Avhich the organism does not neces- 

 sarily require. In fact, under certain circumstances very different 

 substances can cause an acceleration of activity. * * ^ These 

 and similar phenomena obviously arise from different causes. Partly 

 it may be a matter of physiological counter reactions, which can also, 

 for example, occasion an increase of respiration, of circulation of the 

 protoplasm, etc., in response to injurious or other action. In other 

 cases a more simple chemical acceleration of reaction may be con- 

 cerned, as in catalytic action." 



' Journ. Coll. Sci. Univ. Tokyo, 13, 141 (1900). This author experimented with 

 various species of algae and fungi in order to determine their reaction to minute 

 quantities of the sulphates of zinc, nickel, iron, and cobalt as well as to sodium 

 fluoride, lithium nitrate, and potassium arsenate. He found a marked increase in 

 the total amount of vegetable matter produced in the presence of any one of these 

 substances, the increase in the c?se of algae being due, however, to the stimulation 

 of vegetative reproduction rather than to any marked increase in the size of indi- 

 vidual plants. The optimum dose for algae is considerably smaller than that 

 for fungi, 0.0001 gram molecule in most cases proving toxic to the former. Zinc 

 sulphate exerts the greatest stimulating effect. These salts (especially ZnSO^ 

 and NaFl) tend to hinder the development of spores in fungi. Copper sulphate 

 and mercuric chloride stimulate the growth of fungi, but not of algae. 



^See all the papers of this author cited in the Bibliography. 



^ It is probably worth while at this point to call attention to the fact that in 

 nearly every case where this stimulative effect has been observed, electrolytes 

 have been used which are known to show marked hydrolysis, with the formation 

 either of hydroxyl ions, or more generally, as in the case of salts of the heavy 

 metals, of hydrogen ions. And it may well be that, as in the studies of Loeb, the 

 stimulating effects observed by former investigators may rightly be ascribed in 

 the majority of cases to the presence of these ions. 



^ Jahrb. fiir wiss. Botanik, 28, 238, 239 (1895). 



