Journal of Agricultural Research 
Vol. V, No. 5 
186 
reinoculation were depended upon to check the work. In many cases 
transfers of the original strains or of the reisolated ones, or of both, and 
of any intruders were made to raw, sterile cut potato blocks. 
The identification of the closely related species of Fusarium employed 
in this work involved the careful preparation, purification, and morpho¬ 
logical study of high cultures. The nutrient media found of most value 
in obtaining such cultures are as follows: Potato cylinders, rice, stems 
of cotton (Gossypium spp.), and sweet clover (MelUotus alba). Agar 
media were never used, except for plating. As emphasized by Dr. Wol- 
lenweber, the vegetable media are very valuable for encouraging char¬ 
acteristic development of species of Fusarium. 
The control tubers were carefully examined for rot about the wounds. 
These tubers usually remained as sound as when placed in the incubator, 
only 4 out of some 140 used as controls having any rot whatever. 
Sprouting of the inoculated tubers and controls demonstrated their con¬ 
tinued viability. 
Throughout the incubation periods a maximum humidity was main¬ 
tained, and necessarly the ventilation was bad. Readings of the tem¬ 
peratures were taken twice daily, and this factor is indicated by the 
average of all readi es obtained from the particular compartment dur¬ 
ing the stated period. The temperatures were not constant, varying a 
degree or two above and below the average, but the average as recorded 
represents very nearly the actual storage temperature, since such fluc¬ 
tuations as occurred were of a temporary nature. 
It may be considered by some pathologists that the method is an 
extreme one* f hat ^nder the given conditions any organism might be 
expected to cause a rot. It is believed, however, that the conditions 
maintained are no more extreme than those to which potato tubers are 
frequently subjected in field and storage. The following facts tend to 
establish the validity of the method: (1) Certain organisms—for example, 
F. moniliforme Sheldon, F. martii (sensu strict.), Verticillium albo-atrum 
Reinke and Berthold, and Sporotrichum flavissimum Link—did not cause 
a rot under these conditions (see p. 201). (2) F. solani , F. vasinfectum , 
a species of Mucor, and one of Rhizoctonia were doubtfully wound-para¬ 
sitic (see p. 192). (3) The wounded controls remained sound except in a 
few cases where they were in contact with badly rotted tubers; the 
same organism was isolated from such controls as from the inoculated 
tubers in the same compartment. (4) The species of Fusarium herein 
reported as wound parasites grow and rot sterile cut potato blocks in 
pure culture; none of the intruding organisms (bacteria or fungi) were 
able to do this, except, that in a few cases the submerged part of the 
block was attacked. These facts, in addition to the experiments, seem 
to warrant the conclusions reached. 
Since the tubers inoculated with the several species of Fusarium were 
treated uniformly and the rots developed by the respective species were 
