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Journal of Agricultural Research voi. xxv, No. « 
to a depth of i inch at the higher temperatures fell about i ° below that 
of the surrounding water. The reverse condition was found true for the 
soil at the lower temperatures of g° and 12 0 C. This relation is of im¬ 
portance, as the greater amount of damage to the stems of both the pea 
and the bean occurred within the first 2 inches of surface soil. 
In preliminary experiments, the fungus used was found to attack 
vigorously the tissues of the stems of both the pea and the bean. Under 
severe conditions, it proved to be able to attack, and even destroy, the 
plumule and the cotyledons of the young seedlings, and often severely 
damaged the secondary roots arising from the developing hypocotyL 
The lesions produced on the stems were observed to vary in depth and 
area from mere browning and slight destruction of the epidermis, to exten¬ 
sive and ugly ulcers sufficiently deep practically to sever the stem. As in 
the earlier work with the potato, it was found that the number of stems 
showing injury gave no true index to the degree of damage caused by 
Corticium vagum on these plants at the various temperatures. With a 
view to obtaining a more accurate expression of this relation, all the 
diseased plants occurring at each of the various temperatures were 
divided into three separate classes: Slightly injured, severely injured, 
and cut off. 4 The percentage of plants found in these three classes were 
then multiplied by the units 1, 2, and 3, respectively. Quantitative 
values thus determined are included in the various tables under the 
caption, “Intensity of injury.” 
TEMPERATURE STUDIES WITH THE PEA 
Prior to starting the temperature studies on the pea, the author had 
observed a series of experiments conducted by Dr. F. R. Jones with 
respect to the relation of soil temperature to the nature and type of lesion 
caused by Corticium vagum on this particular host. This work 5 con¬ 
sisted of growing five separate crops of peas in soil inoculated with the 
sterile stage of Corticium vagum at a depth of 1 inch and at temperatures 
of 9.5 0 , 12.2°, 15 0 , 18 0 , 20.5 0 , 23.5 0 , 26°, and 28° G. The first four of 
these experiments are interesting primarily in the fact that the steam- 
sterilized soil, regardless of the manner of inoculation, gave results which 
were so exaggerated in severity as to render them valueless for obtaining 
reliable temperature data. The seedlings, Jones states, were so promptly 
and vigorously attacked that only at the extreme high and low tempera¬ 
tures did the plants succeed in getting through the soil. 
In growing the fifth crop Jones used unsterilized pasture soil, proved, 
by preliminary tests, to be free from parasitic strains of Corticium vagum . 
This he inoculated with one-fifth its weight of the infected soil used in 
the previous tests. Four cans for the growth of peas were maintained at 
each of the eight temperatures indicated in the table. Two of the cans, 
at each temperature, containing inoculated soil were planted with seven 
peas each; a third can with inoculated soil was planted with an equal 
number of cotton seeds; the fourth can, containing uninoculated soil, 
* In the first group, slightly injured , were placed all plants showing distinct lesions but not damaged to 
such an extent as to interfere with continued growth. In the second class, severely injured , were included 
such plants as showed injury severe enough to definitely injure the plant in its subsequent growth. In the 
group, cut off, were included all plants with plumules destroyed and those with stems severed by the fungus 
subsequent to infection. 
6 The results of these experiments were compiled by Dr. Jones in the form of a report now on file in the 
department of plant pathology at the University of Wisconsin and are summarized here with his approval. 
The additional work of the author with the pea as presented here must be considered as a continuation of 
that begun by Dr. Jones. 
