11 



The check plants remained sound. 



Subsequently this experiment was carried out in the tropical' 

 house, in a warmer and moister atmosphere. The results of the in- 

 oculation were, however, the same as before, a slight local rotting, 

 followed by a gradual drying up of the infected area. 



It seems that although the Swede turoip is not wholly immune : 

 yet it has considerable natural innnunity from this disease. This is 

 proved partly from the experimental date above presented, and partly 

 from the fact that we found very little disease among Swede turnips 

 ffrowino- in the fields ; although on our own grounds, some lots of 

 Swede turnips were growing along>,ide white turnips which were 

 very badly infected with the disease 



Series X. 



In this series, two white turnip plants and two cauliflower plants 

 were watered with about half a litre of water in which a bouillon 

 culture of the Bacillus oleraceae had been poured. This watering 

 was again repeated two days later and all the plants, including two 

 check plants, watered without the addition of culture were kept under 

 ob.servation for about five weeks. No disease developed in any of the 

 plants, which seems to indicate that the Bacillus oleraceae does not. 

 gain entrance to the plants through the root hairs. 



One of the turnip plants of this series was subsequently inocu- 

 lated at the crown and rotting followed in the course of a few days, 

 thus showing that the turnip plant is susceptible to the disease. 

 Series XI. — The Virulence of Old Cultures. 



In order to test the pathogenic power of old culture, both a cauli- 

 flower and a white turnip were inoculated with an agar culture of 

 the rot bacillus, 2 1-2 months old, being the seventh transfer after 

 isolation.* The cauliflower was inoculated, by means of needle pricks, 

 in the leaf, and kept in warm, moist place. In three days the first 

 sians of rottino- were noticed and the disease subsequently ran its-, 

 usual course, ending in the complete destruction of the plant. 



The turnip was inoculated with a puncture at the crown, which, 

 gave rise to the rotting and final destruction of the plant. 



Summary : These experiments prove that the bacillus is able to- 

 retain its virulence, for a considerable length of time, in artificial agar 

 cultures. 



♦ I have since tried the virulence of cultures which have been on agar for more than 18 

 monthK The cultures produced the characteristic rot in inoculated plants. 



