Dec. io, 1917 
Flaxwilt 
603 
vessels can be seen. Wilting may be due to the combined action of 
several factors: (a) Destruction of the young active root system by the 
fungus, which cuts off a part of the food and water supply of the plant, 
(b) Use of the food and water supply of the plant by the fungus, (c) 
More vigorous growth of the fungus and increased transpiration of the 
host plant due to a rise in the temperature, (d) The possible pro¬ 
duction of toxins by the fungus which injure the host protoplasm. 
(5) F. Uni penetrates the resistant flax plant and stimulates division 
and cork wall formation in cells adjacent to those attacked, but is not 
able to invade the tissues to any considerable extent owing to a number 
of possible reasons: (a) The permanent chemical composition of the re¬ 
sistant plant may be of such nature as to be injurious to the fungus, 
(b) The protoplasm of the resistant plant may be more highly sensi¬ 
tive than that of the susceptible plant, thus reacting more readily in 
the production of those phenomena which cause wilt resistance. (3) 
The stimulation to new cell division and the laying down of cork walls 
which seem to serve as a barrier to further invasion by the already 
weakened hyphae. 
(*6) Wilt resistance in flax is an inheritable character which is appar¬ 
ently determined by multiple factors. 
(7) There is a great difference in the individuality of plants of a strain 
with respect to the resistant character, as shown by their offspring. 
The first generation from some crosses is entirely resistant, from some 
intermediate, and from others entirely susceptible. 
(8) The degree of resistance shown by a strain of flax depends to a 
considerable extent on the environmental conditions under which the 
plants are grown. A strain which was bred to resist under certain con¬ 
ditions may break down under a more severe environment. Plants of 
North Dakota Resistant No. 114, the best strain employed in this work, 
was not entirely resistant with the high summer temperatures in the 
greenhouse. 
(9) All parent strains to be used in crossing should be thoroughly 
tested on infected soil under favorable disease conditions before making 
the crosses. The resistant parent to be used in the cross should be grown 
on infected soil. 
(10) Hydridization experiments should be conducted under uniform 
environmental conditions in order to obtain conclusive results. The 
fact that such varied results were obtained in this work is probably 
due to the different environments under which the plants were grown. 
