30 BOTANICAL GAZETTE [JULY - 
Leitgeb*3 has shown that for the germination of liverwort 
spores a certain intensity of light is necessary, and my experi- 
ments with moss spores show that the same thing is true, only 
to a less marked extent. In experiments which I conducted 
with Marchantia polymorpha spores, parallel with the cultures of 
moss spores, where all were exposed to the light in the middle 
of the laboratory, the different behavior was very marked. The 
moss spores germinated in the usual length of time and without 
any apparent modification due to the weakness of the light. 
The Marchantia spores, on the other hand, showed a very | 
remarkable retardation in germination, and when germination 
did. occur only a long, narrow filament was produced, which. 
gave no indication of the formation of the thallus according to 
the ordinary method of growth in sufficiently intense illumina- 
tion. Other cultures were made and exposed to a much weaker 
light, a room in the Institute basement with only one window 
being used. First, cultures were placed on a shelf at a distance 
of about three meters from the window, then at two meters, 
and then in the window itself. The cultures at a distance of 
three and two meters from the window showed a complete 
failure of the spores to germinate, although they produced 
chlorophyll to some extent. Those which were grown in the 
window germinated after the ordinary length of time. That 
the spores remained capable of germination was shown by the 
fact that they began growth as soon as they were exposed to 
normal illumination. These experiments then show that under 
ordinary conditions of temperature and food supply, the moss 
Spores require a certain intensity of light for germination, but 
that the required intensity is not as great as in the case of the 
liverwort spores. These facts were demonstrated for the three 
species of mosses mentioned above. ! : 
Reasoning from the results which I had already obtained 
with fern spores, a series of experiments was carried out in 
which cultures of spores were exposed to different temperatures: 
The failure of the spores to germinate in the dark is due, as has 
3 Loc. cit. 
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