294 A Bacterial Disease of Turnip (Brassica Napiiis) 



he had also seenjthe leaves drooping but that the seeming recovery of 

 the fohage was due to new growth from secondary crowns. At the 

 College farm the writer found intermixed in tlie drills along with diseased 

 roots numerous healthy-looking plants possessing brown, dry, empty 

 cavities with no sign of the pasty mass ever having been present; such 

 plants invariably harboured slugs or their ova. These plants had, like 

 the types of diseased roots already described, either the young foUage 

 at the growing point destroyed or the foliage of the apical bud had 

 entirely disappeared with the wound thus formed completely healed and 

 surrounded by luxuriant fohage from secondary crow^ns. 



The Nature of the Disease. 



With a view to determine the nature of the pasty mass in the core, 

 small quantities of it, taken from several affected plants were placed 

 in a httle sterile water in a watch-glass. Microscopic examination of 

 the turbid water showed isolated cells and cell-clusters floating in the 

 liquid. There were no traces of protozoa such as are described by 

 Priestley or of fungal hyphae. A small quantity of the liquid taken up 

 on a sterile platinum looji and smeared on a cover-glass showed when 

 stained a dense mass of bacteria. Cultures were then prepared for 

 isolating the organisms. 



Methods. 



The sterihzation of apparatus and media was effected in the usual 

 way. In the first instance nutrient gelatine acidified to 1 per cent, 

 normal hydrochloric acid was employed but this medium w'as found 

 unsuitable; then turnip-juice gelatine of natural acidity and neutralized 

 was also used. Growth on these media, however, proved so inferior to 

 that produced on beef-extract-peptone-gelatine neutrahzed with sodium 

 hydrate that this was exclusively employed in the preparation of pure 

 cultures. Precautions were taken to ensure its constant composition and 

 uniformity of treatment in sterihzation. 



Diseased plants from which cultures were to be taken were thoroughly 

 washed free from soil and placed for 15 minutes in a weak solution of 

 corrosive subhmate. Without removing the chloride the- roots were cut 

 open with a sterile knife from root-tip to crown, the root being inverted 

 in order as far as possible to avoid contamination with foliage epiphytes. 

 Petri-dish cultures were then carried out in the usual way and the 

 several colonies transferred to agar-slants. 



The next step was to prepare sterile blocks of turnip for inoculation 

 from the agar-streak cultures. By means of a platinum hook inocidations 



