Livingston : Chemical stimulation of a (.keen alga 1") 



$u 10,000, with some acceleration of zoospore production in n/l,- 

 000 to 5// 10,000. The acceleration is not as marked as in most 

 of the other salts, however. Normal growth occurs in nj 10,000 

 and weaker solutions. 



1 j. Lithium sulfate (Li 2 SOJ. — A thorough test of this salt 

 was not made, but as far as the experiments were carried the re- 

 sults agree well with the data given for the nitrate. 



iS. Magnesium nitrate (Mg(NO. i ) 2 ). — This cation is present in 

 the nutrient medium. The experiments consisted in increasing 

 its amount. 5///100 does not kill, but produces the palmellaform 

 as does also u/100 and, to some extent, 5;/ 1000. Zoospore 

 acceleration occurs in nj 100 and the normal behavior is exhibited 

 in «/i,ooo and still weaker solutions. 



/y. Magnesium sulfate (MgSOJ. — This salt agrees with the 

 nitrate perfectly excepting that it was impossible to establish a 

 true zoospore acceleration here. Sometimes this phenomenon 

 appears and at other times not. It appeared most often at n'\oo 

 concentration. Perhaps undissociated molecules have to do with 

 this response, but no particular study was made here, this subject 

 lying rather in the field of nutrient salts than in that of toxic ions. 



20. Nickel nitrate (Ni(NO a ) 2 ). — A concentration of ;^/io,000 

 produces death. Filaments are hardly at all present in 5;// 100,000, 

 practically all of the cells being of the other form, but in nj\ 00,000 

 there is about an even mixture of the two forms. A rather slightly 

 marked zoospore acceleration occurs in nj 100,000, and still less 

 marked in weaker solutions. At a concentration of nj 1 0,000,000 

 the alga is certainly uninfluenced by the poison. The zoospore 

 acceleration grades almost imperceptibly into the normal produc- 

 tion of these bodies. 



21. Potassium nitrate (KNO s ). — This salt is so common in 

 the environment of plants that it would hardly be expected to 

 produce very marked stimulation responses. It is probably less 

 toxic toward plants in general than any other salt. At a concen- 

 tration of 5«/ioo the palmella form is produced. This is perhaps 

 due, in part at least, to osmotic phenomena. No acceleration of 

 zoospore production was observed. 



22. Potassium sulfate (K 2 S0 4 ). — As far as could be deter- 

 mined, this salt acts exactly like the nitrate. 



