5§4 
Journal of Agricultural Research 
Vol. XI, No. i 
fungi appeared but not in so great an abundance as the parasitic form. 
Most of the root hairs and very small roots were left in the soil when 
these plants were removed; therefore the fungus obtained in these 
experiments came mainly from the larger roots, which were perhaps less 
likely to be penetrated than the smaller roots. Table II gives the results 
of these isolation experiments. It will be noticed that roots plated out 
on February 21, 1916, gave a much lower percentage of F. Uni than did 
the others. This is probably due to the fact that these plants were 
grown in midwinter, when the soil was cooler and the fungus less vigorous. 
Some of the plants of the resistant strain succumb to the disease in the 
summer, when the temperatures are high; therefore we should be more 
likely to find the fungus in the roots under summer conditions, as infec¬ 
tion is more abundant. 
Table II. — Isolation of Fusarium Uni from roots of resistant flax plants 
Bate. 
Period of 
treatment 
with mer¬ 
curic 
chlorid. 
Number of 
plant roots 
plated out. 
Number of 
roots show¬ 
ing growth 
of F. lint. 
Oct A TflT C . 
Minutes. 
2 y 2 
2 l / 2 
C 
7 
7 
. * * . 
Oct. 7. TQTC ' . 
0 
7 
0 
7 
Feb. 21,1916 . 
16 
4 
Sept. 20, 1916. 
O 
c 
12 
12 
Sect. 26. 1016. 
5 
28 
23 
^ This table shows that the fungus is at least able to penetrate deep 
enough beneath the surface of the resistant plant to protect it from the 
mercuric chlorid used in disinfecting the surface, but does not give any 
evidence as to the extent of invasion. 
Parts of the roots of resistant flax plants which showed brown-spotting 
were fixed in Flemming’s medium fixative, embedded, sectioned, and 
stained with “Pianeze Illb stain” ( 24 ) as previously described. This 
stain gives a pink color with the parenchyma cell walls of the host and 
with the fungus tissues. With lignified, cutinized, and suberized tissues 
it gives a fight green. A careful study of these sections showed that 
the fungus entered the parenchyma tissues of the resistant plant (fig. 8), 
but seldom, if ever, penetrated so far as the xylem elements. This 
limited invasion by the fungus is accompanied by a number of cellular 
changes on the part of the host tissues which are in the immediate 
vicinity of the invading hyphae. 
(1) There is a slight breaking down of the invaded cells which, how¬ 
ever, is not sufficient within itself to disconnect the hyphae from sur¬ 
rounding cells. Marryat (17) and Ward (25) state that in the case of 
wheat which resists yellow-rust (caused by Puccinia glumarum) there 
is a sudden breaking down of the first cells to be invaded, thereby cutting 
