56 
Journal of Agricultural Research 
Vol. XXrV. No. 1 
^ Cabbage seedlings have been found to lend themselves fairly well, dis¬ 
tinctly better than the larger plants, to these studies. The reasons for 
this are that (i) the symptoms of the disease become evident very soon 
after the seedlings emerge from the soil and diagnosis is easy and sure for 
the experienced observer; (2) the experiments can, therefore, be carried 
to definite conclusions within a relatively short time; (3) for such a brief 
period the seedlings develop well in fairly crowded plantation so that 
adequately large numbers can be used in pot culture; (4) the seedlings 
behave well under a reasonably wide experimental range of variation in 
soil temperature and soil moisture. 
INFI.UENCE OF TEMPERATURE UPON THE GROWTH OF FUSARIUM 
GONGLUTINANS IN CULTURE 
A partial knowledge of the influence of temperature upon the growth of 
Fusarium conglutinans has already been obtained. Gilman { 8 ) in his 
early work found that the conidia did not germinate within 72 hours when 
exposed at 8° to 10° C. in Van Tieghem cells, while only 3 hours were 
required for germination at 33° and 8 hours at 21°. His study of the 
growth of the mycelium was limited to a narrower range of temperature. 
The mycelium grew slowly at 8° to 10° and most vigorously at 25°, the 
highest temperature used in his series. An intermediate growth rate was 
obtained at 18"^ to 22"^. It is seen that data on the upper limits of tem¬ 
perature were still lacking; therefore, it seemed advisable to determine 
these limits before taking up a study of the relation of soil temperature to 
the occurrence of yellows. 
A fragment of mycelium from a young culture of Fusarium conglutinans 
was placed in the center of plates (10 by 100 mm.) of 2 per cent potato- 
dextrose agar, titrating +10 Fuller’s scale. The plates were then placed 
in incubators at a series of temperatures ranging from 7® to 37° C., those 
at the higher temperatures being inclosed in moist chambers to guard 
against inhibiting desiccation. Two plates were carried at each tem¬ 
perature, and measurements were made daily for seven days. The results 
at the end of four days and those at the end of seven days are given in 
Table I and are also shown graphically (fig. i) for comparison with the 
percentage of yellows. 
Tabi^iS I .—Growth of Fusarium conglutinans at different temperatures on potato agar 
Temperattjre. 
Diameter of colony at various ages. 
4 days. 
7 days. 
*’C. 
Cm. 
Cm. 
7 to 8 
No growth. 
Slight growth. 
II to 12 
O- 5 
I. 6 
17 to 18 
1-3 
2.9 
21 to 22 
I. 6 
3-5 
24 to 25 
3-2 
6. 0 
27 
3*3 
6. 0 
30 
I. 2 
2. d 
35 
•3 
. 6 
37 
No growth. 
No growth. 
