Aug. 4,1923 
Systemic Infections of Rubus with Orange-Rusts 
229 
Sections of this runner at various points in 30 feet of its course showed no 
mycelium, and as the only rusted plant connected with this long root 
was the one farthest from the parent, it is clear that the fungus was in 
this case unable to go back along the root to any appreciable distance, 
the mycelium having made but little progress beyond the root crown in 
either direction. 
PRIMARY INFECTION SOMETIMES MANIFESTED ONLY THROUGH ROOT SHOOTS 
Attention is called to a type of infection the origin of which is not 
perfectly clear. The plant, 357 A, appears to have been originally 
infected so near the base of the shoot that the fungus soon reached the 
horizontal root, where a slight fusiform enlargement 2 or 3 inches long 
was developed. The shoot grew into a normal cane which showed no 
rusted leaves May 5, 1922. Instead, three new shoots, thoroughly 
infected, had grown up from the root a short distance from the old cane 
(fig. 7). The buds at the base of this cane show that the fungus was 
Pig. 7. —Early invasion of root by mycelium from a point originally somewhere near A' results in root 
infection stimulating growth of shoots B. B' Old cane. A, is normal except for buds. A', which are an 
indication of the presence of hyphae in that part of the cane. 
present in that part which was beneath-the soil. The buds would 
probably have remained dormant, or at least developed only late in the 
season. The growth of infected shoots on the root at each side of the old 
cane is against the supposition that the fungus entered the root first 
through some slight wound, then traveled up the basal part of the cane. 
The root had given rise in the course of 4 feet to five separate normal 
shoots, so there is no reason to doubt that the rust now present came as 
the result of sowing sporidia. A clear-cut case of direct root infection will 
be described later. 
NEW SHOOTS FROM ODD CROWNS SUSCEPTIBLE TO INFECTION 
The cases of artificial infection previously described in this paper were 
of plants which in 1921 were shoots from root runners. In cultivation it 
is the practice to destroy most of these root shoots which spring up 
between the rows or between the hills. There is no attempt to destroy 
the old crown; thus new canes must arise year after year from parts 
