Dec. 10, 1917 
Flaxwilt 
579 
showed stomata on the parts which were below the soil surface; therefore 
it is possible that stomatal penetration is a source of infection as well as 
root-hair penetration, and the penetration of the epidermis of young 
roots. The fungus is also capable of infecting through wounds, as was 
shown by artificial inoculations (Table I). This discovery of root-hair, 
epidermal, and stomatal penetration bears out Bolley’s assumption that 
the fungus is able to penetrate the young plant at any point. 
RELATION OR THE FUNGUS TO THE SUSCEPTIBLE PLANT 
The relation of fungi to their host tissues is a very complicated one 
which varies greatly, according to the fungus and host under considera¬ 
tion. The object of this work was to study the relation of the fungus 
to the various tissues of the host and to seek any evidence that might 
be of value in explaining the possible cause for certain disease phenomena. 
Fig. 4 .—Fusarium Uni entering stoma of young flax seedling in test tube culture. 
Alter entering the susceptible plant, the fungus passes directly through 
the cell walls of the parenchyma tissues to the vascular system, which 
it invades to its limits. Bolley (4) states that sections through the stems 
and roots of wilted plants show that the parasite is able to penetrate the 
cell walls at any point and pass directly through any of the tissues, not 
excepting the woody parts. This statement holds true especially for 
plants in the later stages of wilt. Very few fungus hyphae can be found 
in the cortical tissues of the stems of plants which have just wilted, 
although these tissues become thoroughly ramified with hyphae as the 
plant begins to decay. The cortical parenchyma of the roots, however, 
is the first tissue to be invaded by the fungus. In the early stages of the 
disease the hyphae are confined largely to the woody tissues in the stem. 
Eight newly wilted plants ranging from half-grown to the late-flower¬ 
ing stage were stripped of their foliage, treated for five minutes in a 
1-to-1,000 solution of mercuric chlorid, washed in sterile water, cut in 
pieces with sterile instruments, and plated out on potato agar. Each 
piece was noted carefully, in order to be sure just what part of the plant 
it came from. Pure cultures of F. Uni were obtained from all parts of 
23717°—17-1 
