a. 
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352 BACTERIA IN RELATION TO PLANT DISEASES. 
is sufficient and this is perhaps the best method. An extra supply of knives will allow of 
* sterilization without loss of time. For the same reason, in setting out bulbs the greatest care 
should be exercised not to wound them. 
On May 20, 1883, Wakker removed the foliage from 17 bulbs when the leaves began 
to show signs of the disease. On September 26, only one of these bulbs was diseased. The 
other 16 were potted and bloomed the following April, and the bulbs were still sound when 
re-examined in June. This experiment was repeated by him several times with the same 
result. It was also tried by some of the Dutch growers with entirely confirmatory results. 
There can be no doubt, therefore, that early removal of infected leaves will preserve the 
bulb from infection. This shows very clearly that bulbs are often infected from the leaves. 
The writer believes that natural infection also takes place through the flower cluster and 
that insects will be found to be carriers of this disease. 
A clue to the best method of eradicating the disease is afforded by the fact that these 
plants show a marked difference in susceptibility, some varieties contracting the disease 
readily and others being entirely or nearly immune, as shown in the remarks under Etiology. 
If we can depend upon the statements respecting susceptibility there is good ground 
for thinking that many resistant varieties with other desirable qualities might be originated 
by cross-breeding and selection. The future of hyacinth growing on infected lands in 
Holland depends to a considerable extent, it would seem, on taking advantage of this fact. 
I can not think of any better means of eradicating this disease than by the origination of 
varieties which are not subject to it. This can probably be accomplished by using for 
one parent hyacinths which are not subject to this disease, and for the other those having 
other desirable qualities. From their progeny, for continued propagation, should be selected 
only those kinds which combine resistance to disease with other good qualities. In this way 
it is likely many resistant varieties of desirable character could be originated, but only at 
a very great outlay of time and trouble, since it requires about 7 years to grow bulbs from 
seed to a size suitable for market. The work of originating and fixing desirable strains 
would probably require several decades and were best done by the Government or by 
expert propagators, subsidized by the growers. Meanwhile diligent search should be made 
to know whether it is not possible to reduce the amount of the disease by the discovery 
and destruction of some insect carrier. 
PECUNIARY LOSSES. 
The writer knows nothing very definite as to the extent of the losses in the Netherlands. 
His only guide is the general statement of Dr. Wakker that it is one of the most serious 
diseases of the bulb in Holland, and statements made to him in Holland in 1906. The 
disease continues to be wide-spread and does much damage every year (p. 341). The 
majority of the fields are infected and there is no opportunity for shifting to new fields 
because there is only a small amount of good hyacinth land in Holland, and practically 
all of this is occupied.* 
HISTORY. 
The disease has been known in Holland for a long time, but Wakker was the first to 
ascribe it to bacteria. Fora full abstract of his papers see American Naturalist, 1896. The 
most important are in Dutch. No other Dutch writer has done much with the disease. 
*The best soil is a gray sand with a sandy subsoil and the soil-water within a foot of the surface. Heavier soils 
and soils with water at greater depths are not well adapted to the hyacinth. 
