16 Livingston : Chemical stimulation of a green alga 



2j. Rubidium sulfate (Rb,S0 4 ). — The plant is killed by 77/100 

 and to some extent by 5;// 1,000. In 577/1,000 and 77/1,000 the 

 palmella form is produced, with few or no zoospores, and the cul- 

 ture becomes normal at u 10,000. No acceleration of zoospore 

 production occurs here. 



2 ./. Silver nitrate (AgNO s ). — Death occurs from 7//1 00,000 

 to 677 1 .000,000. Filaments do not appear in 77 1,000,000, but 

 begin to survive in 577/10,000,000, where also there is an increase 



17 



Figure 16. Palmella and filaments from 5;/ ,'10,000,000 AgN0 3 . 



Figure 17. Normal filaments and zoosporangia (a), from ///jo,ooo,ooo AgN< >... 



in the number of zoospores. The cultures are normal or slightly 

 accelerated as to zoospore activity, in 77/10,000,000. (See figs, 

 ij, 16, and 1 j. The former shows typical palmella form in 

 77/1,000,000, the second a mixture of palmella and filamentous 

 forms in 577/10,000,000, and the last a normal filamentous culture 

 in 77 10,000,000. Zoosporangia are shown at a.) The limits are 

 quite sharply defined for this salt. 



2j. Sodium nitrate (NaNO a ). — This cation is but little more 

 poisonous than potassium. The palmella form is produced in 



