12 BOTANICAL GAZETTE [JANUARY 
plants; and second, that which deals with the higher plants. The 
studies of toxic agents on algae and fungi, while they bear upon the 
present paper only indirectly, frequently furnish valuable data for 
comparison. Unfortunately the determinations have been made 
with different ends in view, and have been tabulated in such a way 
that only here and there can the most general comparisons be made. 
LIVINGSTON (23, 24, 25) has made perhaps the most valuable 
contribution to this work on the lower plants. His experimentation 
takes into consideration many toxic salts; determines their killing 
concentrations as well as the strengths which cause changes in vegeta- 
tive character of the alga Stigeoclonium. He also attempts (25) to 
correlate the work of previous authors with each other and with his 
own. 
Fungus growth and spore germination as affected by toxic salts 
in solution was studied by CLarK (8). Since it is generally recog- 
nized that Cu(NO,), and CuSO, have very nearly the same if not 
identical toxic limits for a given plant (25, p. 18), it is interesting to 
note from this table: 
Aspergillus in Cu(NO,). dies in 252/100 
Sterigmatocystis in CuSO, dies in 125”/1000 
Penicillium in Cu(NO,). dies in »/1 
Oedocephalum in Cu(NO,), dies in 156”/10000 
Botrytis in Cu(NO;), dies in 313%/10000 
Thus Penicillium will endure approximately four times as much 
copper as Aspergillus; eight times as much as Sterigmatocystis; 
thirty times as much as Botrytis; and sixty times as much as Oedo- 
cephalum. 
According to STEVENS (39) many metallic salts affect spore 
production in fungi. Among these Cu(NO,), and CuSO, inhibit 
spore formation at a lower concentration than any of the others tried 
by him, the response occurring at »/1oo in Penicillium. 
The response of acceleration of growth of plants as caused by 
toxic elements in solutions has been studied in conjunction with the 
response of death. There seems to be a general agreement among 
authors that zinc is the most active stimulating agent to vegetative 
growth. Yet the concentrations at which ZnSO, are said to produce 
most marked acceleration are far from agreeing. Thus, RICHARDS 
mgr 
