64 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
while there are others who maintain that the disease never appeared 
until new varieties were introduced in their collections. At first 
sight it certainly appears that the newer varieties are more addicted 
to the disease than the older ones. This may possibly, however, not 
be the case. When a grower brings new bulbs into his stock which 
was previously clean, he runs great risk of introducing eelworms. As 
very frequently it is the newer varieties that are added — and the bulbs 
may appear perfectly healthy — these new varieties are usually regarded 
as being more susceptible and so accounting for the spread of the 
trouble. If certain varieties prove to be immune we have a possible 
means of attacking the problem. Webber, Orton, and others in 
America have endeavoured successfully to breed varieties of cowpea 
and other crops resistant to root -knot. It is perhaps a problem similar 
to that of rusts of wheat, where Biffen found that immunity is a 
recessive Mendelian character. Simple selection ought also to be 
practised ; if in a field of Narcissus badly infected with Tylenchus 
certain of the plants remain outstandingly free, it would probably 
pay to begin propagating bulbs by offsets from these plants. The 
question of how such a common species as Tylenchus devastatrix 
suddenly became rampant amongst Narcissus bulbs is one of those 
problems which often face pathologists in general. Where did the 
variation occur, in Narcissus, in Tylenchus, or in both ? Was it so 
sudden as most of us imagine ? 
There is much I should like to say regarding methods of cultivation, 
such as depth of planting, aspects, lifting annually, as against leaving 
the bulbs in the ground for two or more years, ripening, storing, forcing, 
etc., but the time at my disposal will not allow of it. 
Many bulb-growers look upon the disease as " one of Nature's 
gifts," and are of the opinion that the bulbs will ultimately right 
themselves. The latter part of the statement opens up the whole 
question of health and disease in general. Suffice it to say that if the 
bulbs are left to right themselves, the bulb industry in Narcissus will 
soon cease to .exist. 
[The investigation of this Narcissus disease was undertaken jointly 
by the Royal Horticultural Society and the Imperial College of Science 
and Technology.] 
