40 



Investifjatioii of Bnlh Rot oj Narn'sstfs 



is washed out in alcohol till the plant tissue is almost colourless. By 

 this method the eggs and worms are stained a bright red and are seen 

 as easily in thick as in thin sections. 



The infected leaf slowly dies from the tip downwards, and the eel- 

 worms, both mature animals and larvae, migiate into the lower portion 

 of the leaf within the bulb. The dead upper portion of the leaf falls 

 on to the ground and if the weather is sufKciently warm the eggs hatch 

 and young larvae are soon liberated in the soil through wliicli they can 

 pass to a healthy bulb. Cold weather makes the eelworms sluggish, 

 or dormant, or even kills them, and consequently checks infection. 



Having once entered the bulb, either through the old leaf bases 

 or the young foliage, the eelworms pass slowly downwards to the " plate" 

 leaving the scales discoloured as a whole or in part. If such a diseased 



J-kJ 



Fig. 2. Eelworms in tissue of bulb scale, x 300. 



bulb is cut across transversely the discoloured scale is seen as a brown 

 ring or part of a ring (Fig. 3). If cut longitudinally the diseased scales 

 appear as clearly marked brown stripes (Fig. 4). It is generally the 

 case that bulbs which have a discoloured scale have also an unusually 

 luxuriant root system. 



When the eelworms reach the plate they leave the scale down which 

 they have travelled and enter another scale uj) which they make their 

 way. Thus they are able to reach the green blades again. Blades 

 infected in this way look quite healthy till they suddenly fall over and 

 die. Such a stage is reached in about the month of June when whole 

 masses of leaves may fall within a week. It is obvious that this falling 

 of the foliage is not due to any new outbreak but merely marks a stage 

 in a disease which has been present in the bulbs for many weeks. 



As the season advances the diseased bulbs contain an increasing 

 number of eelworms, eggs, and larvae. When such bulbs are removed 



