[Vor.8 
316 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
which is strikingly supported by a relatively high H-ion con- 
centration. In various forms, notably in Penicillium and Fusar- 
ium, and under certain conditions, secondary maxima at or near 
the neutral point occur, and these often approach in magnitude 
the primary maxima on the acid side. It is not necessary, of 
course, to assume that the H-ion concentration most favorable 
for germination will also prove most favorable for the continued 
growth and development of the organism. In this work, it was 
found that germinating spores of P. graminis conspicuously 
exhibit only rudimentary germ tubes or knob-like projections 
HI /00 I 
vs uM at m^ al Vy 
S v 
xD 
3H 80 
rs 2 Mannite + fs Beet Decgctron \ 
wg Manne + 34|Beef Dedoclion 
60 
Puy 1 2 3 * 5 6 7 8 3 
Fig. 12. Aspergillus niger in a medium composed of M /5 mannite and sugar 
beet decoction (25?C.). 
6624 per cent mannite + 3314 per cent sugar beet decoction. 
3314 per cent mannite + 6624 per cent sugar beet decoction. 
in the most alkaline nutrient cultures included within the favor- 
able range and that all of the fungi show abnormal and irregularly- 
shaped germ tubes in the most acid cultures allowing germination, 
indicating, therefore, that such reactions while favorable for 
germination are unfavorable for growth. The germ tubes of 
B. cinerea disintegrate at Py 2.1. 
Nutrient media for pathological and bacteriological work are 
usually neutral or slightly acid, while my data show that increas- 
ing concentrations of hydrogen 1 ions from neutrality to approxi- 
mately Pa 3.0—4.0, in the various culture media, favorably influence 
the germination of the spores of B. cinerea, A. niger, P. cyclopium, 
P. italicum, P. graminis, L. saepiaria, and Fusarium sp. How- 
ever, with increase of hydrogen-ion concentration above this 
zone, the germination quantities abruptly diminish and soon 
reach a zero value. Under conditions of moderate active 
