GALLS CAUSED BY FUNGI 
I 2 I 
Galls caused by Mycetozoa 
There are certain organisms which occupy neutral ground 
on the borderland of the Animal and Vegetable Kingdoms. 
They form the group known as Mycetozoa, or Fungus- 
animals. In one stage of the life-cycle they exhibit affinities 
with plants, in another they approach more nearly to the 
Protozoa. At least two species give rise to galls on the 
plants which they infest. The best known is Plasmodiophora 
brassicae, a species which gives much trouble to gardeners 
and farmers, causing the only too well known “ finger and 
toe ” disease of Turnips, Swedes, Cabbages, and other 
cruciferous plants. It usually attacks the root, giving rise 
thereon to nodular or warty outgrowths. Sometimes the 
entire root is swollen, clubbed, and distorted (see Leaflet 77, 
Board of Agriculture). Another mycetozoon gall structure 
may be seen in Plate XVI., Fig. 2, which delineates the 
stem of the Germander Speedwell with tumours caused by 
Sorosphaera verotiicae. The life-history of this parasite 
resembles that of Plasmodiophora brassicae. The spores, 
however, are united in a hollow sphere ; in P. brassicae they 
are free and regularly formed. Blomfield and Schwartz 
described in detail the life-history in Annals of Botany , 
January, 1910, and observed : “ We have been successful in 
producing tumours by sowing Veronica seeds in a pot and 
sprinkling them with water containing the sporospheres 
from dried tumours pounded with a pestle in the water. 
There was no evidence of any disease in the roots, many 
of the young roots being examined microscopically with 
reference to this possibility ; for this reason, doubtless, the 
parasite does little damage to the host plant; its effect is 
largely local, and we find no such destruction as that caused 
by Plasmodiophora in Cabbage plants.” I am indebted to 
Dr. Blomfield for the galled plant figured in the plate. 
