INVESTIGATIONS ON THE NARCISSUS DISEASE. 6l 
necessary in order to treat the soil by the greenhouse method, and it 
is doubtful if the treatment would be beneficial. Small areas or beds, 
especially those to be occupied with seedlings, might be profitably 
steam-sterilized by the inverted-pan method. Sterilization with 
chemicals such as formaldehyde, toluol, carbon bisulphide, naptha- 
lene, &c, offers possibilities of cleaning infected ground, but the larger 
the area the greater are the difficulties to be contended with in effectu- 
ally carrying out the treatment. 
The treatment oj bulbs by soaking has received much attention.* 
Last autumn about 3,500 diseased bulbs and the same number of 
healthy ones were treated in dozens with a large number of different 
chemical solutions. The minimum time for soaking was 18 hrs., and 
the maximum 96 hrs., with periods of 24, 48, and 72 hrs. intervening. 
In most cases different strengths of the same chemical solutions were 
employed, as it is evident that where the bulb is damaged by a liquid 
that liquid cannot be employed. Eighteen hours was taken as a 
minimum time, as it was thought that no solution could penetrate the 
bulbs sufficiently in less time to be effective. All the bulbs were topped. 
Recent observations show that the bulbs have been killed in some in- 
stances ; at any rate there are no signs of growth at the present time. 
The warm-solution treatment of bulbs has been tried, and healthy 
and diseased bulbs have been soaked in water and chemical solutions 
of various strengths for 1, 2, and 4 hours and at a temperature of 43- 
44 0 C, 46-47 0 C, and 49-50 0 C. in each series. Healthy bulbs soaked 
in water and chemical solutions at the last-named temperature have 
been materially damaged, but the experiments are such that the results 
cannot be recorded until the bulbs are lifted. 
Hewitt recognized some time since that Tylenchus was connected 
with the disease, and in a paper entitled " Eelworms in Narcissus 
Bulbs," published by the Department of Agriculture and Technical 
Instruction for Ireland in 1912-1913, recommends soaking the bulbs 
in copper sulphate solution at a strength from 5 J per cent, to 7 J per cent, 
for 17 hrs. On a recent visit to Ireland it was understood from one 
firm who had worked in conjunction with Hewitt that the treatment 
advised had been abandoned as the results did not prove satisfactory. 
Hewitt died in the midst of his investigation, and the published 
pamphlet is a record of his unfortunately uncompleted work. 
Coupled with the warm-solution treatment, a series of experiments 
were performed with the Reichert thermal stage, by means of which 
apparatus it is possible to record, with some degree of accuracy, the 
length of time an eelworm is capable of life at a fixed temperature. 
Between 43 and 44 0 C. all eelworms were killed at the end of 45 minutes. 
At a temperature between 48-49 0 C. the eelworms succumbed at the 
end of 15 minutes ; 52-53 0 C, 11 minutes ; 53-54 0 C, 9 minutes ; 
55-56 0 C./9 minutes ; and 57-58 0 C, 5 minutes. The effect of tem- 
perature on the eggs was not considered. 
No matter in what manner the bulbs are treated, it is courting 
* See p._65. 
