14 Livingston : Chemical stimulation of a green alga 



not entirely to be attributed to the cation. This would agree with 

 the results of certain other authors to be cited later. (Fig- 14 

 shows palmella and dead cells from 3/// 100,000.) 



1 y. Iron nitrate [ferric) (Fe 2 (N0 3 ) fi ). — The cells are all killed 

 at w/io.OOO. They live as the palmella form in concentrations of 

 from 8/// 100,000 to 5;//ioo,ooo. At 7^/100,000 and 8;/.'' 100,000 

 zoospore production is accelerated, and at 2^/100,000 and 7//100,- 

 OOO the growth is normal for weak solutions. For these tests 

 iron was omitted from the nutrient medium to which the poison 

 was added. 



ij. Lead nitrate (Pb(NO a ),). — Death ensuses in #/ 10,000. 

 In 5^/100,000, the majority of the cells die, but some become of 



15 



Figure 14. Palmella and several dead cells from 3/7/100,000 H 2 S0 4 . 

 Figure 15. Palmella from «/i, 000,000 AgNQ 3 . 



the palmella form. The latter form is maintained through the 

 series to 5 n\ 1,000,000, in which solution there are usually a num- 

 ber of good filaments, although most of the culture is of spherical 

 cells. Zoospore acceleration occurs in «/ 100,000 to 5 «/ 1,000,000. 

 In 7// 1,000, 000 to 5 /z/ 10,000,000, the growth of filaments and 

 zoospores is the same as in the control. 



16. Lithium nitrate (LiN0 3 ). — Many, but not all, of the cells 

 die in 5/// 100. The palmella form is produced from 5;// 100 to 



