552 
Journal of Agricultural Research 
Vol. XIV, No. 12 
Two schematic drawings have been prepared for the purpose of indi¬ 
cating in a general way the path followed by the infecting plasmodia and 
the direction of infection in the different tissues (fig. 1,2). These draw¬ 
ings apply equally well to both root and stem. The arrows are meant 
to show schematically the general course taken by the parasite as it 
passes in through the tissues and produces a typical club. (The actual 
path along which the infecting plasmodia travel can not, of course, be 
represented by straight 
lines.) Besides showing 
direction of infection, the 
arrows also indicate the 
extent to which the differ¬ 
ent tissues become in¬ 
fected. The cambium is 
represented by lines with¬ 
out arrow heads. The 
arrow lines running par¬ 
allel to it indicate in each 
case the direction of in¬ 
fection. 
Each of the two fig¬ 
ures represents one half 
of one end of a club. In 
order to obtain such a 
portion the club is cut 
transversely through its 
thickest part. Then one 
of the ends is split longi¬ 
tudinally in half. Figure 
1 illustrates the infection 
of a rather young root 
or stem, while figure 2 
shows the infection of a 
somewhat older organ. 
It will be seen that, al¬ 
though the course taken 
by the parasite in the 
Fig. i.—D iagram showing the course taken by the infecting 
plasmodia in a young cabbage root or stem. The arrows indi¬ 
cate the direction and extent of infection. 
two cases is the same, the extent of infection is somewhat less in 
old plants. In the old root or stem the vascular elements are well 
developed, and the parasite does not penetrate so deep into the tissues 
on either side of the cambium. In young organs where the vascular 
elements are not so well developed the plasmodia pass deeper into the 
tissues on either side of the cambium. The diagrams show the para¬ 
site entering the host tissue at the points where the arrow lines pass into 
the cortex. From this point it spreads to the sides and downward and 
