12 
Research Bulletin No.'p 
by the offensive odors of bacterial rots, producing a blackening 
and softening of tissues which extends a considerable distance 
beyond the actual site of the organism. This was demonstrated 
microscopically and culturally. At times, however, especially 
in cold, dry conditions, a dry rot as typical as that produced by F. 
tricJiothecioides was produced. F. trichotJiecioides invariably pro- 
duced a dry rot with only a very limited darkened zone extending 
beyond the destroyed zone, made up of large cavities and a mixture 
of disintegrated, dry; shrivelled tissue and fungus tissue. No 
darkening extended beyond the actual site of the fungus and no 
softening of tissue occurred. Microscopic examination revealed 
the fact that F. tricJiothecioides attacked the tissue intracellularly 
and destroyed each cell completely before it proceeded to the 
neighboring cell, while F. oxysporiim attacked the tissue intercellu- 
larly at first, and then attacked the cells intracellularly, but not 
until the tissue had been blackened and disorganized. In this way 
a softened tissue withotit cavities was produced. These rots pro- 
duced experimentally with pure cultures of F. oxysporum lend sup- 
port to the observations and conclusions of Smith and Swingle 
(35), }^Iaxxs (24), who report the occasional appearance of black 
specks in the parenchyma of tubers infected with F. oxysporum, and 
Tones (17), who attributes stem end rot of tubers to the activity of 
this organism, although they may have dealt with "Mischarten." 
Sherbakoff (33) reports certain strains of species of Elegans 
(using the section as a morphological group) to be tuber rotters. 
He distinguishes between Fnsariiim spp. that are tuber rotters and 
such as are vascular element inhabitants.^ 
(2) EXPERIMENTAL INFECTION OF LIVING PLANTS 
A series of experimental inoculations of healthy potato plants 
with F. oxysporum and F. trichothecioides were carried out, in an 
attempt to determine whether or not F. trichothecioides is unable to 
lAfter these experiments had been concluded and this paper written, a 
paper by Carpenter (7) has appeared. This represents a wholly independent 
although simultaneously conducted piece of work. The results of Carpenter 
make it quite probable that the observations made by the writer on a few 
strains of F. o.vysponini are of quite general application, since he arrives at 
the same conclusions for numerous though different strains of F. oxysporum. 
His conclusions as to the method of attack by the fungus and the nature of 
the rot are practically identical with the —-iter's. 
