Nov. 1007.] 



KUSANO.—PHOBO-GHEMOTAXIS OF MYXOMYCETES. 147 



able a ring that it can be recognized even by the naked eye as 

 a thin white cloudy ring not essentially deforming after one 

 hour or more. 



The structure of the ring — diameter, breadth and the features 

 of both inner and outer margins— are not similar in the case of 

 all acids used at an equimolecular concentration in a tube of 

 equal diameter. After 10-20 minutes sulphuric acid forms the 

 largest ring, 4-5mm. in diameter while with hydrochloric and 

 nitric acids it is slightly smaller. Among the organic acids, 

 oxalic acid forms a ring nearly similar to that produced by the 

 strong mineral acids above cited. Acetic, citric, malic, lactic 

 and formic acids give rise to smaller rings, while the smallest 

 and most obscure ring is obtained by tartaric acid. 



The thinnest and sharpest ring is formed with sulphuric 

 acid. The breadth of the ring ranges to 0.2— 0.25mm. Outside 

 and inside this extent the number of spores suddenly decreases, 

 and the demarcation of both outer and inner margins of the 

 ring is very definite. Other mineral acids form similar rings. 

 With organic acids it is somewhat different. Oxalic acid forms 

 a sharp ring but with greater breadth (0.3— 0.4mm.). Acetic 

 acid forms a ring of nearly equal breadth to that formed by 

 oxalic acid, but the margin is not sharply demarcated. Malic 

 and citric acids always form a ring with obscure margin. The 

 thickest but most faint ring is formed with tartaric acid. 



From the numerous instances of ring-collections given by 

 various kinds of organisms we may distinguish two cases as 

 indicating their cause To such an agency as oxygen, light, 

 temperature or undissociable chemical substance the organism 

 assembles at the zone of optimal concentration, while at the 

 infra- and supra-optimal concentration of the same agency a 

 respective attraction and repulsion may take place. 1} In the 

 case of chemotaxis with dissociable substances, however, w r e 

 must take into consideration the components that may exist in 

 the solution. The investigations of Buller 2) and Shibata 3) 



1 ) EOTHERT, IOC. Clt. 



2 ) Buleer, Ann. of Bot. XIV. 1900. p. 548. 



3 > Shibata, Jahrb. f. wiss. Bot. XIL. 1905. p. 561. 



