376 OLDENBUSCH: STIMULATION OF PLANTS 
the ions dissociated in the solution and of the undissociated 
molecules, then the physiological properties of a solution are due 
to the same factors. The authors worked out this theory with 
lupine seeds, the germination of which was accelerated by dilute 
solutions of electrolytic salts. They claimed that this stimu- 
lation was due to the hydrogen and metallic ions in the solutions. 
Heald (8) working with seeds of other plants obtained similar 
results and also attributed them to the electrolytic dissociation. 
Stevens (9) working with fungus spores applies this same theory. 
Iwanoff (10) claims that metallic salts are poisonous to plants in 
proportion to the atomic weight of the metal, the heavier metals 
being more poisonous than those of smaller atomic weight. In 
his opinion, the same is true of the alcohols, the lower alcohols 
(methyl and ethyl) being less poisonous than those of higher 
molecular content, such as propyl and butyl. Steinberg (11), 
in a recent paper on the stimulation of Aspergillus, attributes the 
stimulation to the increase in H ion content when zinc salts are 
added to the nutrient solution. It is not obvious, however, 
that the action of such oligodynamic substances is due to the 
hydrogen ion concentration alone, especially since we find non- 
electrolytes, such as ether, chloroform, and other anaesthetics, 
exerting a stimulatory influence. Carbon disulphide, being a 
very volatile liquid, which is non-dissociable in aqueous solution, 
~ also comes in this category. 
Various authors have worked with ether and chloroform, 
although few have done anything with carbon disulphide. Town- 
send (12) in his experiments with Avena seeds found that if 
dormant seeds were exposed to a moist concentrated atmosphere 
of ether for a short time, or to a weaker atmosphere of ether for a 
longer period, the seeds germinated sooner and grew more rapidly 
than under normal conditions. This acceleration lasts for some 
time and gradually disappears. Ina later paper (13) Townsend 
verified his results with other seeds: Zea Mays, Cucurbita, 
Phaseolus, etc. He also found that dry seeds, exposed to an 
atmosphere of HCN gas (14), germinated more rapidly than 
those not exposed although this advantage did not last for any 
appreciable time. Miss Latham (15), working with Sterigmato- 
cystis nigra, determined that cultures of the fungus grown on 
nutrient media and exposed to chloroform vapor, produced a 
more luxuriant growth with a greater dry weight than similar 
