3 
While nothing of the nature of haustoria was observed, it was plainly 
evident that the presence of this abundant mycelium was the cause of 
the disease, for wherever the threads of the fungus reached, there were 
darkened cell walls and lifeless contents. No fungous ferment was ob¬ 
served, and it is probable that as with the Hymenomycetes described by 
Hartig* as attacking forest trees, none exists except at a very limited 
distance from the tips of the liyphse. 
In the intercellular spaces, and often in the cells themselves are found 
numerous olive bodies, which for want of a better name we have called 
olive conidia. These olive conidia are most abundant in old specimens 
where the decay has progressed well into the potato, and although oc¬ 
casionally almost wanting, are generally easily observable. Where 
present in large quantities they give a decided greenish brown tint to 
the tissue. 
Upon the exterior of the diseased area are often found, though some¬ 
times in limited numbers, together with an occasional olive conidium, 
delicate hyaline spores borne on aerial kyphse. So far the hyaline 
spores have not been seen in progress of formation within the tissue of 
the potato, but upon the blackened sprouts as they are grown in the 
hotbed they are present in abundance, arising from the tips of elongated 
liyphse. 
A third form of the fungus shows itself both upon sprout and root 
in the shape of flask-like pycnidia with elongated beaks or necks fim¬ 
briated at the apex. Often the globular bodies of the pycnidia are 
buried in the tissue of the potato, and only the slender necks are visi¬ 
ble above the surface, giving it a bristly appearance. 
Where specimens covered with pycnidia are protected from the rains 
the pycnospores collect in a more or less firmly united mass at the apex 
of the neck, and the fimbriations seem to serve the purpose of a basket 
for the mass. The appearance of the fimbriated slender necks and sur¬ 
mounting yellow globules is very characteristic. 
Although not certainly connected with the species of fungus causing 
the black rot there have been found, often in badly diseased specimens, 
immense numbers of glob ,Jar sclerotia differing in structure from those 
of many other species but surrounded by and evidently made up of 
hyphai identical with those of this species. These sclerotia were found 
in all stages of formation and in the last stages in such abundance as 
to entirely fill the tissue of the diseased potato, causing it to become 
gray and finally charcoal black. 
DESCRIPTION OF CULTURES. 
The growth of this parasite upon underground stems composed 
largely of carbohydrates suggested the idea of cultivating it upon arti¬ 
ficial media. In doing this, numerous points of interest were brought 
* Die Zersetzungsersclieinungen des Ilolzes 1878, Berlin, Die Lekrbucli der Baum- 
krankheiten. 
