E. J. Welsford 37 



Infection Experiments. 



A series of experiments was begun in September, 1915, on bulbs 

 grown in cold frames at the Imperial College of Science and Technology, 

 and in prepared beds at Chelsea Physic Gardens. It was found, however, 

 that more trustworthy results would be obtained if the bulbs could 

 be grown under better conditions, such as those obtaining in the larger 

 nurseries. For this purpose, Messrs Barr and Sons were good enough 

 to provide facilities, and since March, 1916, experiments and observa- 

 tions have been carried out in their fields and drying sheds at Taplow. 



Infection with Bacteria. 



Infection experiments were carried out with seven strains of bacteria 

 which had been isolated from diseased bulbs and grown on either 

 Narcissus or potato-mush agar. Healthy bulbs were planted in 

 September, 1915, and were infected with pure cultures of the several 

 strains in the following month. A piece of the bulb was cut out with 

 a sharp sterilised scalpel and a portion of agar with the bacteria was 

 placed at the bottom of the pit, after which the piece of bulb was re- 

 placed. Healthy cut and uncut bulbs were planted as controls. When 

 the plants were examined in the following spring and autumn, they were 

 all found to be quite healthy. 



The experiments were repeated during May and June, 1916, but 

 again with negative results. 



It was, therefore, concluded that the bacteria which had been isolated 

 from the scales of diseased bulbs were not the cause of the disease. 



Infection with Fusarium bulbigenum. 



This fungus was isolated from diseased bulbs and grown on sterilised 

 potato-mush agar, it grew vigorously and produced conidia of the 

 Monosporium and Diplocladium types. A series of experiments was 

 then made; sixty bulbs of the varieties Narcissus Leedsii, Narcissus 

 bicolor Barri conspicua. Narcissus incomparabilis Cynosure, were cut 

 and infected with portions of agar bearing Fusarium. The Fusarium 

 was used in three stages: (1) rapidly growing non-fruiting mycelium 

 from the edge of a culture ; (2) mycelium bearing conidia of the Mono- 

 sforium type, and (3) mycelium with conidia of the Diplocladium type. 



In every case the bulbs remained perfectly healthy, though the fungus 

 was often found growing between the dead outer scales of the bulb. 

 There was no indication that the fungus had any action on healthy 

 bulbs. The examination of a large number of bulbs leads to the 



