GALLS CAUSED BY FUNGI 121 



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 veronicae. The life-history of this parasite 

 resembles that of Plasmodiophora hrassicae. 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. 



