36 BOTANICAL GAZETTE [ybLy 
sure within the spore could not have been the operative force in 4 
bringing about germination 4 
The absence of any effect from osmotic pressure was also 4 
rendered probable from the experiments in which the spores 7 
were supplied with either glycerin or potassium tartrate. Spores 
of the three species above mentioned germinated readily in” | 
1 and 2 per cent. solutions of glycerin in the light, but in the 
dark they remained unchanged. Glycerin is a non-nutritive — 
substance for the moss-spores, and at the strength used would | | 
be about osmotically equivalent to the sugar. In the 1 per cent ‘ 
was the same in the light as in the control experiment. In the 
dark cultures supplied with 0.5 per ccnt. potassium tartrate there 
was a complete failure to germinate. The isotonic coefficient of 
potassium tartrate is 399”, and consequently the osmotic value of 
the last solution would not be far from that of 2 per cent. graj 
sugar. Cultures of spores which were supplied with a 2 
cent. solution of lactose, also non-nutritive for the moss spore 
showed the same failure of germination in complete darkness 
The spores which were exposed to light germinated howevs 
with as great readiness as in the control experiment, where t 
were exposed to ordinary conditions. | 
It is known that certain substances like iron chloride an 
cobalt salts, when used in a solution which is too dilute to I 
growth is presumably due to a so-called catalytic action. 
fact suggested the possibility of calling forth germinatio 
the dark by means of such substances, and to this end the 
lowing experiments were performed: Spores of the species 8 
erally used were grown in different strengths of iron chlo i 
* DE Vriks, Jbid. 506. 
