TOXICITY OF HEAVY METALS 83 



activity which occur with A1(NO 3 ) 3 are: (i) the formation of a dark body 

 occupying about half of the spore, (2) the formation of a small local 

 swelling at one end of the spore, and (3) the development of one or more 

 appressoria, the latter sometimes having their characteristic dark color and 

 sometimes being hyaline. Unless the formation of the internal dark bodies, 

 which seem to arise directly through protoplasmic activity, may be taken as 

 evidence of a penetration of the toxic salt, no information as to whether 

 A1(NO 3 ) 3 actually enters the spores was obtained. 



Nickel. 



Nickel nitrate proved to be very slightly toxic to these fungus spores, its 

 effect on germination being manifest only in very high concentrations. On 

 this account no study was made of the possible influence of calcium and 

 magnesium nitrates upon this toxicity. 



The toxic effects of Ni(NO 3 ) 2 

 alone may be added here. A con- 

 centration of o.5m inhibited ger- 

 mination. In a concentration of 

 0.25111, numerous local swellings of 

 the spores were observed. Both 

 local swellings and normal germina- 

 tion were present in a 0.12501 

 solution of this salt, and germina- 

 tion was perfectly normal, as in 

 the distilled water control, where 

 a concentration of o.o5m or lower was employed. Germinating spores in 

 o.25m concentration of Ni(NO 3 ) 2 frequently exhibited a granular appear- 

 ance such as has been described for spores in solutions of Cu(NO 3 ) 2 which 

 were not quite concentrated enough to inhibit all activity. 



Fig. 6. Germinating spores 

 o.oo2m Al (NO 3 ) 3 , X 650. 



from 



TOXICITY OF SINGLE SALTS 



The present section will be devoted to the relative degrees of toxicity 

 exhibited by the various substances heretofore dealt with, together with 

 certain other considerations bearing upon the problem of chemical stimu- 

 lation as evidenced in the simple solutions employed in these studies. Besides 

 the substances already mentioned, nitric acid entered into the experimen- 

 tation, and the information gained regarding the toxicity of this substance 

 will also find place here. 



From what has preceded it appears possible to group the effects of the 

 different treatments into four distinct kinds of physiological response on 

 the part of the fungus spores here employed, (i) a given treatment may 



