July 29, 1918 
Potato-Stem Lesions 
219 
penetrating the stem to a considerable depth, invaded the vascular 
bundles in one instance. Subsequently dark-brown discoloration devel¬ 
oped and the organism was recovered in pure cultures from the petioles * 
of the topmost leaves. 
CONCLUSIONS 
(1) Neither Rhizoctonia solani Kuhn nor any particular species of 
Fusarium can be held as the sole agents responsible for the familiar stem 
and stolon lesions of the potato. 
(2) Several parasitic species of Fusarium, as well as Altemaria, Botrytis 
Sderotinia, Zygorhynchus, Corethropsis, Phoma, Clonostachys, Acro- 
stalagmus, and probably other fungi, should be included with certain 
strains of Rhizoctonia in the group of the causal organisms. 
(3) While this group of parasites may be quite large, a number of strains 
of Rhizoctonia, along with other saprophytic species, are associated with 
stem lesions which are unable to attack the underground portions of the 
potato plant. 
(4) The lesions produced by some of these fungi, while practically insep¬ 
arable by their macroscopic characters when produced under natural 
field conditions, show distinct characteristics peculiar to certain strains 
or species when reproduced under control conditions in the greenhouse. 
