THE JOURNAL 



OF THE 



BOARD OF AGRICULTURE 



Vol. XVII. No. 8. 



NOVEMBER, 1910. 



ON THE OCCURRENCE OF "CROWN-GALL " IN 



ENGLAND. 



During the present season, examples of plum, rose, 

 raspberry and chrysanthemum plants have been received at 

 Kew for investigation, each bearing irregularly globose, 

 nodulose galls or swellings originating from the crown or 

 collar region of the stem. The galls varied in size from a 

 pea to that of a cricket ball, and one gall at the base of 

 a rose stem measured seven inches in diameter. Small galls 

 were in some examples also present on the branches of the 

 root. Most of the galls were in an exolete or woody con- 

 dition, and gave no indication of the true cause of their 

 formation. Mycelium was present in some instances in the 

 dead tissues, and various conidial conditions of fungi were 

 not uncommon in the crannies present on the surface, but 

 nothing of a nature that suggested, from analogy, an 

 organism capable of inducing the formation of a gall. 



It was not until a batch of Chrysanthemum frutescens, L., 

 having the base of the stems covered with large excrescences, 

 1 was examined, that the true nature of the gall was discovered. 

 This proved to be the well-known and very destructive disease 

 called "crown-gall " in the United States. The galls are 

 caused by Dendrophagus globosus, Tourney, one of the 

 Myxogastres, allied to Plasmodiophora brassier, Woronin, 

 the cause of " finger-and-toe " or "anbury" on the roots of 

 many cruciferous plants. When a section of a gall in active 

 growth is examined under the microscope, strands of 

 Plasmodium are seen permeating the tissues of the gall in 

 every direction. Eventually the plasmodium concentrates 

 in the peripheral cells forming the gall, and from thence 



