542 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
The organism was increased for inoculation purposes by being grown on 
steamed rice in Erlenmeyer flasks, inoculations of these cultures being made 
with a spore suspension from the original tube cultures. It generally re¬ 
quired a period of about three weeks for the macroconidia to be produced in 
abundance, hence the flask cultures were incubated for three or four weeks. 
Equal quantities of a very heavy water spore suspension made from the rice 
cultures were poured over the surface of the soil and very thoroughly ad¬ 
mixed. The soil had been previously allowed to dry enough so that the 
amount of suspension added would bring the soil to a good condition for 
planting. 
The experiment was started on January 13. On January 28, when the 
plants were just putting out the first true leaves, they were thinned out to 
50 plants in each flat. The experiment was continued until February 16. 
During this period the temperature in the greenhouse was maintained quite 
constantly at 26 to 28° C. Much of the time, however, cloudy weather pre¬ 
vailed; consequently the light relations were poor and the plants grew 
slowly. 
Toxic effects on the growth of the plants in flats no. iA were very marked, 
as was expected. Germination was delayed three days, growth was very 
slow, and none of the plants attained the size of those in the other flats. 
Many of the plants died from undetermined causes, though a considerable 
number developed typical symptoms of the wilt. On account of the diffi¬ 
culty in most cases of determining whether the death of the plants resulted 
exclusively from wilt infection, an accurate count was not attempted. 
The first symptoms of \yilt appeared on February 7, when several of the 
plants were found to have wilted during the day. When the plants were 
examined, the dark discoloration of the vascular system was very plainly 
evident. It was noted throughout the course of the experiment that pre¬ 
liminary symptoms of leaf yellowing were seldom manifested. Plants 
apparently healthy when examined in the evening would be found com¬ 
pletely wilted by the next morning, or such wilting was sometimes found to 
have taken place during the day. In all cases it seemed evident from ex¬ 
amination of wilted plants that infection occurred quite early in the life of 
the seedling. The primary xylem was always found to be discolored, 
though in many cases discoloration of the vascular system did not extend 
very far above the surface of the ground. A prominent symptom observed, 
however, was a stunted condition of the plant. For several days, usually, 
no other symptom was noticeable, but all such plants finally wilted, and the 
vascular system showed the typical discoloration. 
Wilted plants were removed each day for examination. In case of any 
doubt as to the cause of the wilting, platings were made to determine the 
presence of the fungus. A few of the plants were destroyed by “damping- 
off” fungi or by other causes. Such plants were discarded and were not 
included in the total number of plants in the flats from which percentages 
