Dec. 3, 1917 
Podblight of Lima Bean 
495 
were forming in large numbers in all tubes in the light and in smaller 
numbers in all those in the dark. The ratio between the number of 
pycnidia formed in the light and in the dark remained nearly constant, 
the fruiting bodies forming in all tubes, but they were better developed 
in the light. In one week spores began to exude from the pycnidia 
both in the light and in the dark. From this time spores continued 
to be exuded, but here again the amount of the exudate was relatively 
less in the dark. Toward the close of the experiment, however, there 
appeared to be a relative increase in the exudate from the pycnidia 
formed in tubes in the dark. But one conclusion can be drawn from 
these results, that while the dark retards the production of fruiting 
bodies and accelerates vegetative growth, it is not as marked as the 
results obtained with other fungi by the writer and others. 
INFLUENCE OF TEMPERATURE ON GROWTH 
To determine the influence of temperature on growth 12 (No. 2, 3, 5, 
6, 8, 9, 10, 15, 17, 18, 19, and 20) of the 20 chambers in an Altmann 
incubator were used. Tubes of cooked rice were inoculated with spores 
of the fungus and immediately placed in the chambers, where they were 
kept exposed to the respective temperatures for a period of 27 days, at 
the end of which time growth had practically stopped. No growth took 
place in chambers 2 (4.1 0 C.),'3 (6.1 0 C.), 19 (35.4 0 C.), and 20 (38.8° C.), 
and but a scant growth in 18 (32.9 0 C.). The optimum growth was 
found in chambers 15 (26.5° C.) and 17 (30.5 0 C.). The growth of hyphse 
decreased relatively with the increase and decrease of the temperature 
from these limits of the optimum. In chambers 9 (17.4 0 C.), 10 (19.4 0 
C.), 15 (26.5° C.), 17 (30.5 0 C.), and 18 (32.9 0 C.) stromatic masses of 
pseudoparenchymous tissue were produced which macroscopically looked 
like pycnidia. A careful examination of these bodies, however, showed 
that, while they bore some resemblance to pycnidia, no cavity had been 
produced within them and no pycnospores were found. The cause for 
this was later found to be due to a lack of sufficient aeration, resulting 
probably in a reduced oxygen supply. A subsequent experiment in 
which cultures of the organism on cooked rice were exposed in a chamber 
in which most of the oxygen had been removed by a mixture of pyrogallic 
acid and sodium hydroxid showed that while mycelial growth continued 
under such conditions the production of fruiting bodies was inhibited. 
In addition to the fact that the cultures in the Altmann chambers were 
kept in the dark, the absence of oxygen, which in itself was found, as 
already shown, to reduce somewhat the production of fruiting bodies, 
evidently accounted for the failure to produce pycnidia in the cited cases. 
The growth of the podblight fungus in artificial cultures is schemati¬ 
cally shown in figure 11. 
