9 
INOCULATIONS. 
Healthy potatoes, kept in a moist atmosphere in the laboratory, upon 
being covered with the hyaline conidia and pycnospores of the fungus, 
became, in the course of a few weeks, badly diseased with the typical 
black rot. The fungus is capable of entering the eyes of the potato 
and is nourished by the small, dead fibrils often connected with the 
eyes. In inoculations, the diseased portions began in or near the eye. 
To convince the most skeptical, initials were scratched upon the surface 
of one potato with a sterile needle, and the surface coated with hyaline 
conidia in water. In three weeks the initials appeared in typical black- 
rot lines against the brown back ground. 
PROBABLE LIFE HISTORY. 
The life cycle of the parasite, although not certainly completed by 
these different forms, may cover a period of several weeks and perhaps 
months. The abundant mycelium present in the diseased roots planted 
in the hotbed for the purpose of obtaining sprouts infects the young 
shoots as described. This infection may take place either through the 
medium of spores or by the growth of mycelium from the diseased areas 
themselves. Diseased sprouts planted in the field produce diseased 
roots which may spread the disease to other hills either through the 
soil directly or by means of the numerous fibrils from other plants. 
These infected areas, although perhaps inconspicuous at first, grow 
steadily in diameter not being checked by digging, and when the pota¬ 
toes are stored for keeping continue to grow in the root and at the 
same time to produce the various forms of spores. These reproductive 
bodies when supxilied with sufficient moisture are capable of infecting, 
unaided, sound potatoes througn their eyes. Thus one diseased potato 
when stored in a bin of healthy ones is capable of infecting all those in 
the bin and causing them to rot in a short time. 
To what extent the fungus is able to live upon the dead vegetable mat 
ter of the soil has not been determined, but from its omnivorous habits 
numerous substances might be expected to nourish it in an active state. 
The fact that the parasite grows luxuriantly upon strong nahrlosung 
agar would perhaps indicate its ability to inhabit different stable ma¬ 
nures applied to the potato fields, and although no experiments were at¬ 
tempted to show whether a passage through the digestive caual would 
kill the spores, circumstantial evidence points strongly to the belief that 
such passage does not destroy all forms. 
Geratocystis fimbriata probably winters not only in the roots used for 
seed the following spring, but in the soil itself, upon decaying portions 
of sweet potato roots and other vegetable substances. The sclerotial 
stage mentioned may be found to compose the principal resting stage 
of the parasite. 
PREVENTIVE MEASURES. 
I. The first and most important precaution to be taken in combating 
the disease is to plant only perfectly healthy seed in the hotbed, even 
