10 
if it is necessary to import such. This preventive measure is most 
essential, as diseased seed will give diseased sprouts, which in turn will 
grow a crop of worthless potatoes. 
II. The selection of healthy sprouts is plainly necessary in case the 
fungus gets into the hotbeds, and under no circumstances should dis¬ 
eased plants be put into the field. The test of using copper fungicides 
in the hotbed has not been made, but from analogy seems to promise 
assistance. If the fungicide is used the shoots should be kept green 
with it until pulled. 
III. Fields which have become so impregnated by the disease that 
they refuse to grow profitable crops had best be added to the regular 
farm rotation. This method will, if continued for several years, allow 
the accumulated infective material to burn itself out by consuming all 
available food material in the soil. 
IV. Decaying roots and the refuse after digging should be carefully 
removed from the field and burned, as such debris adds to the food of 
the parasite. 
Y. The use of large quantities of barnyard manure probably favors 
the development of the trouble, since it adds greatly to the decaying 
vegetable matter of the soil. Where the use of commercial fertilizers 
can be made to take the place of manure it will certainly be desirable 
to make the change. 
VI. Although no experiments have yet been completed upon the mat¬ 
ter, it is probable the spread of the disease in the bin may be checked 
by dipping the roots in one of the copper mixtures, preferably the am- 
moniacal solution, before storing for the winter. What effect tobacco 
smoke or the fumes of sulphur would have in checking the disease in 
the bins remains to be ascertained. 
Experiments are now under way to ascertain, if possible, the effect of 
the use of the ammoniacal solution of copper carbonate in preventing 
the disease. Hotbed, field, and bin experiments are in progress, and it 
is hoped definite results will be obtained. 
SUMMARY. 
I. The black rot of the sweet potato, both upon young shoots, caus¬ 
ing “ black shank,” and upon mature roots, is caused by the parasitic 
action of the fungus Ceratocystis ftmbriata. Ellis and Halsted. 
II. Portions of diseased tissue develop, when placed upon various 
media, abundant growths of the parasitic fungus. 
III. Three modes of spore formation are present, two endogenous 
from the tips of specialized hyphse, the third from cyst-like bodies. The 
connection of a sclerotial form, although not demonstrated by culture, 
is strongly suspected. 
IV. Spores grown in cultures are capable of inoculating healthy roots 
through the broken cuticle or through the eyes. 
