464 
Journal of Agricultural Research 
Vol. XXVI, No. 10 
Table I. — Characteristic measurements of spores of Fusarium martii ( App . and Wr.) 
var. pisi (n. var.) from pseudo pionnotes produced in cultures 20 days old 
On oat agar. 
On potato agar. 
On potato agar with 2 per 
cent dextrose. 
Maxima and minima. 
Average. 
Maxima and minima. 
Average. 
Maxima and minima. 
Aver¬ 
age. 
P.ct. 
1 
1 
10 
85 
3 
A* 
9 to 12X2 to 2.5. 
A* 
11X2.4.... 
P.ct. 
12 
S 
29 
54 
A* 
s to 9X2 to 3... 
15 to 27X2 to 4.. 
M 
7X2.3... 
20.4X3.5- 
30.6X4- • 
32X4 2.. 
P. ct. 
S 
• 5 
0 
93 - 5 
1 
M 
6 to 11X 2 to 3. . 
a 
9X2.3 
27 to 37X4^04.5 
33 to 42Xs to 4.. 
31.7X4.3... 
29 to 38X4. 
27 to 37X4. 
32X4 
39X4 
TAXONOMY 
The foregoing description of the fungus causing the stem and rootrot 
of peas corroborates Bisby’s opinion that it belongs in the section 
Martiella of the genus Fusarium, and that it is very closely related to F. 
martii. It is not identical with any of the varieties of that species 
described by Sherbakoff ( 12 ). An opinion must be rendered whether 
the differences found entitle the fungus to a specific rank or whether it 
should be placed among the varieties of F. martii , two of which have 
been distinguished by Sherbakoff on morphological grounds, and one by 
Burkholder (4) by a physiological character, pathogenicity toward 
varieties of Phaseolus vulgaris . 3 Since the fungus in question varies 
greatly in pathogenicity toward species of Pisum, it must be distinguished 
on morphological characters which are constant. It appears to the 
writer that the differences between this fungus and Fusarium martii are 
not greater than those between the species and varieties already de¬ 
scribed by Sherbakoff, and therefore the fungus is considered to be a 
variety. 
HOST PEANTS 
All of the limited number of species of the genus Pisum that have 
been available for study have been found susceptible to infection, at 
least at the base of the stem. No cases of strongly marked resistance 
at this point have been found. The following host list has been studied: 
Pisum sativum Linn. var. arvense, P. sativum Linn. var. saccharatum, 
P. sativum Linn. var. umbellatum , P. elatius Bieb., P. jomardi Schrank. 
Lathyrus odoratus has been slightly infected, but so slightly that it 
does not seem likely that this fungus ever produces an important disease 
of this plant. 
PHYSIOLOGY OF THE FUNGUS 
This variety of Fusarium martii does not appear to possess any unusual 
characteristics in the germination of its spores or in any other functions 
that merit special attention. However, in connection with a study of 
the relation of soil temperature to the development of the disease, it 
became a matter of interest to determine the optimum temperature for 
the growth of the fungus in pure culture. It was grown several times 
in petri dishes on potato agar with 2 per cent dextrose in a series of 
incubators maintained at temperatures that were approximately con- 
• Burkholder (4) has suggested that since Dr. Westerdijk isolated a certain culture of Fusarium martii 
from peas there may be a F. martii var . pisi parasitic upon peas. Such a physiological variety has not 
been demonstrated or described. 
