Apr. 15, i 9 « 
Susceptibility of Injured Seeds to Molds 
105 
disinfected (Pi. 18, A). When it is not sterilized and thus protected 
against infection, the seedling rarely even gets a start (PI. 13). When to 
this chance of injury is added the effect of fungicides on the exposed 
embryos, there is more than sufficient reason for the failure of the plants 
from such seed to get above the surface of the ground. 
HUMIDITY REQUIRED FOR THE GROWTH OF PENICILLIUM AND 
ASPERGILLUS ON STORED WHEAT 
In an experiment to determine the relation of atmospheric humidity 
during storage to formaldehyde injury of wheat, Penicillium developed 
in the stored wheat in the three dampest samples only. The different 
humidities were produced in desiccators containing various mixtures 
of sulphuric acid and water, progressing by intervals of 10 per cent 
from a saturated atmosphere over water to one absolutely dry over con¬ 
centrated sulphuric acid. The composition of the mixtures with water 
necessary to produce these different humidities was determined by Prof. 
C. W. Woodworth ( 24 ).* 
Penicillium first appeared after 10 days on wheat stored in the saturated 
atmosphere and in that containing 90 per cent moisture. The mycelium 
continued to grow luxuriantly in these, and after 16 days it appeared in 
the one having 80 per cent humidity. In none of the drier lots did it 
ever develop, and it never was as abundant in the 80 per cent as in the 
90 per cent and 100 per cent (saturated) chamber. Aspergillus was also 
very prevalent in the 80 per cent humidity but was largely overgrown in 
the other two atmospheres by the greater growth of Penicillium. In 
addition, Aspergillus developed to some extent in the desiccator with 
atmosphere containing fo per cent moisture, indicating that its moisture 
requirements are less than those of Penicillium. 
The humidities produced in the desiccators, and the development of 
Penicillium and Aspergillus in them, are shown in Table II. 
Table II .—Development of Penicillium and Aspergillus on wheal in atmospheres of 
different humidities 
Percentage of humidity. 
Specific 
gravity of 
h 2 so« 
+H2O 
mixtures. 
Penicil¬ 
lium. 0 
Asper¬ 
gillus. 0 
I. OOO 
- + + 
+ + 
I. 070 
+ + 
I. 130 
+ 
+ + 
I. 206 
O 
+ 
1. 2 73 
0 
0 
1. 334 
0 
O 
1. 400 
O 
O 
1. 470 
O 
O 
i- 530 
O 
O 
1. 604 
0 
O 
1. 840 
O 
O 
a The symbols used indicate that the fungus is abundant (+ + ), fairly abundant (+). or lacking (o). 
1 Reference is made by number (italic) to “ Literature cited," pp. 120-122. 
