THE SLIME MOLDS OF OHIO 
7 
I. Sporangia combined into an aethalium, 
K. Sporangia well defined, tubular, with lateral walls entire. 
Family (7) Tubiferaceae (P. 37) 
K. Sporangia poorly defined; walls perforated or frayed into strands 
which may resemble a capillitium. 
Family (8) Reticulariaceae (P. 38) 
H. Capillitium present. Order IV. Trichiales 
L. Capillitium threads solid, coiled or straight, simple or branched. 
Family (9) Margaritaceae (P. 39) 
L. Capillitium threads tubular. 
M. Capillitium of colorless branching wrinkled tubules. Sporangia 
combined into an aethalium. 
Family (10) Lycogalaceae (P. 40) 
M. Capillitium of threads marked by half rings, cogs, or warts. 
Family (11) Arcyriaceae (P. 40) 
M. Capillitium of threads marked by spiral bands or complete rings. 
Family (12) Trichiaceae (P. 44) 
CLASS 1 . PLASMODIOPHOREAE 
Vegetative stage a plasmodium found in the cell of living plants. 
Spores are formed by the plasmodium breaking up into a large number of 
independent cells being massed in the cells either as free spores or united 
into groups. This class includes but a few species distributed among four 
genera. Only one species, that causing the club root of cabbage, will be 
considered here. 
PLASMODIOPHORA. Woronin. Club Root. 
Parasitic in the parenchymatous cells of the roots of living plants. 
The plasmodia fill the cells and cause abnormal growths in the parasitized 
tissue. 
P. brassicae Wor. This parasite effects the roots of cabbage, turnips, 
and other cruciferous plants, causing abnormal growths, often of 
considerable size and of various shapes. These growths interfere 
seriously with the normal development of the plant and sometimes whole 
fields of cabbage are ruined by this disease. When infected roots decay 
the spores are set free and later germinate, forming zoospores which prob¬ 
ably enter new hosts through the root hairs. 
Heavy applications of lime have been found to aid in controlling the 
pest. The best method of control, however, is to grow cabbage on non 
infested land. If ground becomes infested the parasite may be starved out 
if no cruciferous plants are allowed to grow on the ground for three or 
fours years. Especial care should be taken to have the seed bed in which 
cabbage plants are started free from the parasite. 
Common. 
