496 
Journal of Agricultural Research 
Vol. XI, No. io 
INFLUENCE OF TOXIC AGENTS ON GERMINATION OF SPORES 
Perhaps no chemical substance has been more generally studied in its 
relation to the growth of plants than copper salts. This is perhaps due 
to its well-known efficiency as a fungicide, following the discovery of which 
a large amount of work was undertaken to determine the concentration 
of copper salts necessary to prevent germination or bring about the death 
of the spores of a great variety of fungi. Much of this work was done 
with saprophytes, and consequently has little more than a scientific 
interest, while the practical side of the problem was evident from the fact 
that the toxicity to germinating spores of many well-known parasites was 
established. Because of the various uses that chemical substances may 
be put to, such as antiseptics, disinfectants, etc., the toxic action of many 
salts, metals, and acids, 
alone and in combina¬ 
tion, on flowering 
plants and fungus 
spores have been ex¬ 
tensively studied, and 
as a result an extensive 
literature on the sub¬ 
ject has accumulated. 
As might be expected, 
the results have been 
very variable and often 
contradictory. In gen¬ 
eral, however, all in¬ 
vestigations have shown that copper salts, among other chemical 
substances, are exceedingly toxic to all germinating spores and to the 
seedlings of flowering plants. Coupin (ir) has shown by experiments 
that i part of copper sulphate to 700,000,000 parts of water is suffi¬ 
cient to retard the root growth of wheat seedlings, and the writer has 
proved (18) that a small amount of a single alkali salt, such as 
sodium chlorid, sodium carbonate, and magnesium sulphate in water 
cultures, inhibits the growth of the same plant. Heald (22) found 
1/51,200 and 1/25,600 gram-molecule per liter of copper sulphate to be 
toxic to Pisum sativum and Zea mays, respectively. According to Moore 
and Kellerman (26) 1 part of copper sulphate to 500,000 parts of water 
killed Closierium moniliferum in 4 days and 1 part of copper sulphate to 
3,000,000 parts of water killed Anabaena flos-aquce in three days. 
Uroglena americana was even more sensitive and was killed in 16 hours 
in 1 part of copper sulphate to 10,000,000 parts of water. 
These few references show the extreme sensitiveness of some of the 
flowering plants and some algae to copper salts, and at the same time the 
variability in their resistance. Although not strictly comparable with 
C£A/r/G/Z4£>£- 
Fig. 11 .—Diaporlke phaseolorum: Graphic representation of growth on 
cooked rice at different temperatures. 
