267 
Fungi at various Temperatures , &c. 
with more or less their usual vigour when again brought into normal 
atmospheric conditions. Thus the question whether a given concentration 
of carbon dioxide produced absolute inhibition could only be determined by 
experiments lasting a very long time. The incubation time for germination 
in a good nutrient in the neighbourhood of 18 0 varies for the different fungi, 
being as low as 4-6 hours for normal Botrytis spores and as much as about 
one day for spores of Aspergillus repeiis . For most of the fungi used the time 
required for germination in air at ordinary laboratory temperature is about 
eight hours, and thus the period of seven days chosen in the above experiment 
is about 20 times the normal incubation period for germination. A fungus, 
therefore, which fails to germinate under the conditions of the experiment 
in a period 20 times its normal germination period may be looked upon as 
completely inhibited to all intents and purposes. 
In carrying out these observations, an interesting behaviour was noticed 
in the case of germ-tubes of Rhizopus nigricans. In 50 per cent. C 0 2 
spores of this fungus showed universal germination, but the germ-tubes had 
a peculiar appearance. Instead of the normal long straight cylindrical 
hyphae of uniform diameter the germ-tubes here appeared as short stunted 
structures of very irregular shape. In optical section they presented a very 
ragged outline, and their diameter, though varying widely in different parts, 
was much in excess of the normal. The same appearance was observed in 
the germ-tubes in 60 per cent. C 0 2 , but not in those in 40 per cent. These 
germ-tubes were strongly reminiscent of the cell swellings in species of 
Mucorineae described by various workers (Ritter, Wehmer) 1 as ‘ giant 
cells } ( Riesenzellen ). The latter have been shown to be due to the 
accumulation of excess of acid in the culture solution, and it appears 
probable that the formative factor in the present case is acidity due to the 
high pressure of carbon dioxide. On removal of these distorted germ-tubes 
to ordinary air, the}'- at once continued their growth in the normal fashion. 
The following table gives the concentrations of carbon dioxide which 
were found to stop germination at 15-18° over a period of seven days: 
Table V. 
Fungus. 
Spores sown in 
T-E./S. 
Spores sown in 
water. 
Aspergillus repens .... 
40 
— 
Mucor sp. ..... . 
4 ° 
— 
Botrytis cinerea (both strains) 
50 + 
20-30 
Monilia cinerea 
50 4 
20 
Phoma roseola 
50 +• 
20 
Alternaria grossulariae 
50-60 
>30 
Rhizopus nigricans .... 
60 
20 
Botrytis parasitica .... 
60 + 
20 
Sphaeropsis malorum . . . 
60-70 
30 
Fusarium sp . 
80 + 
30 
Penicillium glaucum . . . 
8 0 -95 
>30 
1 See on jthis point Ritter: Jahrb. f. wiss. Bot., lii. 351-403, 1913. Wehmer: Ber. dent. bot. 
Gesell., xxxi. 257-68, 1913. Lopriore : 1 . c. 
