14 Afp‘k‘ulfur(tl Kx periraent Station UeHearcli Bulletin 
scope. Tisdale descTil>es practically the same method in a recent 
j)aper (*J8, p. 570). Under such nnfavoralde conditions, however, 
the host was at a disadvantage, and since a number of other 
s])ecies of Fusariiim penetrated the plants in the same way, no i 
si^niilicance is giATii to the observations. 
In order to determine the relation of the organism Avithin the 
various host tissues, a lar^e number of stained free-hand and 
microtome sections Avere made of stems and roots at A^arious stages 
of deATlopment of the disease. A numl)er of attempts to obtain 
j)ieces of roots at the time of infection Avere, hoAveA^er, unsuccess- 
ful. In Avoody stems, in an early stage of the disease, only the 
xylem tubes nearest the pith Avere found to contain the fungus 
hlaments. llie pith had disappeared in both normal and diseased 
plants of moderate size. Later, other of the tubes thruout the 
xylem area Avere penetrated and had become filled to a large extent j 
Avith a netAvork of fungous filaments. In still more advanced 
stages, all of the xylem elements (fig. 4, II) Avere found to contain 
the fungus, and in addition the cortical parenchyma Avas invaded. 
Many of the fibrous roots Avere destroyed, and figure 5 shoAvs 
hoAv the disease progresses from the smaller root l)ranches into 
the main root. A and C represent the cortex and pith, resj)ec- 
lively. and are, at this stage of the disease, seen to be free from 
discoloration due to the fungus. B indicates the xylem region. 
AAdiich is discolored in areas beginning at the ])oint of origin of 
lateral roots and extending mostly U])Avards. Later the broAvned 
areas become continuous and the xylem is found to be in this con- 
dition thiaiout th(‘ stem and root (fig. '2. C). XeAV roots form, 
but oftcMi of insullicient number to maintain the life of the plant. 
In otluu- cases the ])h\nts subsist Avith a reduced supply. 
It seians, therefore, that the symptoms ]n*oduced result not 
siiu|)ly fi*om (1) a mechanical clogging or (*2) a slow a])propria- 
tion of food and Avater by the fungus, as others have previously 
stated, but that (3) a considerable destruction of the root system, 
aud, |)(M‘lia))s, (4) a rcaluction of the a<*tivilv of tlu‘ protoplasm 
due to the j)ossible presence of toxins seerded 1)V the fungus, also 
aid ill this. 
That other organisms may often facilitate the entrance of 
Fusarlurn is given s[)ecial consideration in another part of this 
pai)(‘r. 
