38 Tnvestiyation of Bulb Rot of Narcissus 



conclusion that Ftisariimi hulbigenuni is very often present on the surface 

 of the dead and dying outer scales of healthy bulbs. It is especially 

 abundant in bulbs which have been injured, but even on rotting scales 

 it seldom penetrates far into the tissues. It is evident, therefore, that 

 the presence of Fusarium bulhigenum is not suificient to account for 

 Narcissus rot. 



Infection ivilh Black mycelium. 



A very dark coloured, almost black mycelium was isolated from 

 diseased bulbs "and a series of infection experiments was carried out. 

 The infected bulbs remained perfectly healthy. It was, therefore, obvious 

 that this mycelium did not cause bulb rot, and no attempt was made 

 to obtain conidia or to determine the fungus. 



Eumerus strigatus and Merodon equestris. 



It has been shown by Fryer (4) that the larvae of these two insects 

 do much harm to Narcissus plants, causing a weak, distorted growth, 

 and the loss of a large number of plants. The damage caused by them 

 is, however, quite distinct from the symptoms known as bulb rot. 



Infection with Rhizoglyphus echinopus. 



These bulb mites are very common on unhealthy bulbs, and are 

 consequently easily obtained for experimental work. The mites were 

 lifted off the diseased bulb with a sable brush and were gently trans- 

 ferred to a healthy bulb, some being put between two injured scales 

 and some between two perfect scales. The bulbs were not planted 

 until the mites were seen to move and were therefore presumably 

 uninjured by the manipulation. These insects undoubtedly do a 

 great deal of harm ; they puncture the scales, and gradually cause 

 their destruction, thus weakening the bulb ; but in no case was bulb 

 rot obtained by the use of Rhizoglyphus ecJiinojms, and it seems, there- 

 fore, improbable that the mite causes the disease either by eating the 

 bulb or by carrying bacteria into its tissues. 



Infection with Tylenchus devastatrix Kuhn. 



During the course of this investigation more than one hundred 

 diseased bulbs have been dissected and in all of them eelworms or their 

 eggs have been found. Small portions of tissue containing live worms 

 were consequently easily obtained and were placed on the "cut surface 

 of the scales of healthy bulbs. Fifty bulbs infected in this way were 

 planted in a box of sterilised soil in October and were kept in a cold 

 frame till the following spring. By the middle of February they all 



