468 
Journal of Agricultural Research 
Vo). XXVI, No. to 
have not only reproduced the disease as it occurs in the field, but have 
shown other effects rarely observed in the field. Chief among these 
is the wilt of seedlings at high soil temperatures consequent upon either 
a complete rotting off of the base of the stem, or more usually an invasion 
of the vascular system of the subterranean portion of the stem by the 
parasite. This invasion, it may be noted, is not in a manner typical of 
vascular parasites, inasmuch as it follows a very extended decay of the 
outer tissues, is somewhat limited in the distance to which it progresses, 
and is often preceded rather than followed by discoloration. When a 
similar decay of cortical tissues is produced by other organisms it is not 
uncommon for any one of a number of species of Fusarium to advance 
as far and produce a wilt. The more important information contributed 
by the temperature studies is an explanation of the varying importance 
of the disease in regions where it occurs, and the aid which this knowledge 
gives in distinguishing the several pea diseases. The disease can not 
become important in most pea-growing sections of Montana, for instance, 
and in regions where the growing season is continuously cool because of 
the low soil temperatures. It can not be the cause of the decay and death 
of plants that often occur in early spring before warm days have arrived. 
This disease requires a higher temperature for its inception than that 
caused by any of the other parasites studied. 
RELATION OF SOIL MOISTURE TO THE DEVELOPMENT OF THE 
DISEASE 
In order to determine whether high water content of the soil increases 
or decreases the rate of development of this disease, one can of inoculated 
soil placed at each temperature in a series similar to that previously 
described in detail, was maintained at about 75 per cent of its water¬ 
holding capacity, while the other cans were maintained at 50 per cent 
of the water-holding capacity of the soil. The plants in the wet soil did 
not show any marked difference in behavior from those in the drier soil. 
Peas have been grown in saturated soil at an optimum temperature for 
the development of the disease. Here wilting seems to take place a 
little earlier than in drier soil, evidently because the damaged tissues 
become water soaked and destroyed by bacteria at a more rapid rate. 
While in the case of this disease, as in the case of others, wet soil promoted 
decay started by the parasite, it does not appear to affect in great meas¬ 
ure the action of the parasite itself. 
VARYING PATHOGENICITY OF CULTURES OF FUSARIUM MARTII 
VAR. PISI 
During an extensive search for this Fusarium in pea-growing districts 
in 1920, an isolation from pea roots grown in the Bitter Root Valley, 
Montana, gave a culture which, when used for inoculation, gave very 
slight infection. Thereupon spores from all of the cultures of this fun¬ 
gus which had been collected were used to inoculate peas under con¬ 
trolled optimum conditions for infection in order to compare their patho¬ 
genicity. The culture from Montana produced but few slight lesions, a 
culture from Maryland caused a mere browning of the susceptible por¬ 
tion of the stem, and a third culture from Madison, Wis., was hardly more 
of a parasite; while nearly all of the plants inoculated with other strains 
were rotted off at the attachment of the seed. Since two of these non- 
