176 BOTANICAL GAZETTE [SEPTEMBER 
by the offensive odors of bacterial rots, :producing a blackening 
and softening of tissue 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. 
trichothecioides was produced. F. trichothecioides 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. trichothecioides attacked the tissue intracellularly 
and destroyed each cell completely before it proceeded to the 
neighboring cell, while F. oxysporum 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 without cavities was produced. These rots pro- 
duced experimentally with pure cultures of 7. oxysporum lend sup- 
port to the observations and conclusions of SMITH and SWINGLE 
(35), MANNs (24), who reports the occasional appearance of black 
specks in the parenchyma of tubers infected with F. oxysporum, and 
Jones (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 Fusarium 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 
* After these experiments had been concluded and this paper written, a paper by 
CARPENTER (7) has appeared. This represents a wholly independent although simul- 
taneously 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. oxysporum 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 writer’s. 
