1 i \ THE BOTANA 'AL MAGAZINE. [Vo i. xxi. No. 250. 



swarm-spores within a short time after sowing, was found to 

 be the fittest material. The experiment was, therefore, made 

 mainly with it, not, however, forgetting the verification of 

 results obtained with the other two species. 



In testing the chemotactic action of the substances I follow- 

 ed mainly the well-known capillary method of Pfeffer. 1 ' The 

 substances used arc pure chemical compounds as well as 

 extracts from vegetable bodies, comprising acidic, basic and 

 neutral, or easily dissociable as well as less or not dissociable 

 substances. 



Nearly all substances used in the experiment act upon the 

 three species of Myxomycetes in an almost similar manner : at 

 moderate concentrations all acidic substances attract, and 

 basic substances repel them, while neutral substances are 

 indifferent, if they are not poisonous like some heavy-metal 

 salts. The intensity of action is proportional to the degree of 

 acidity or alkalicity of the solution in the capillary. 



The acids which were tested by the capillary method amount 

 to twenty one in number. Among these, the attraction of 

 mineral acids is stronger than the most organic acids at the 

 necessary cquimolecular concentration. Generall}', a dibasic acid 

 acts stronger than a monobasic acid. The less dissociable or 

 weak acids, such as tannic, boric and hydrocyanic, show no or 

 only a very feeble action in attracting the spores near the 

 mouth of the capillary filled with them. 



The following table shows the kinds of acids and their 

 respective actions towards the three species of Myxomycetes 

 Here A indicates marked attraction, a, weak attraction and ?, 

 no definite collection, all at cquimolecular concentrations. The 

 case in which no experiment was made is denoted by — . 



. [elhtUium Slemonitis Comatrivka 



Hydrochloric acid A. ..A. ..A 



Nitric acid A ... A ... A 



Sulphuric acid A. ..A... A 



Phosphoric acid A. ..A.. .A 



I'iiiii.i:, Pflanzenphysiologie II. 1,904. p. 709. 





