336 BACTERIA IN RELATION TO PLANT DISEASES. 
anastomosing vascular bundles become yellowed, and where we often find a considerable 
area of the intervening parenchyma yellow and soggy (plate 19, figs. 6, 7). Subsequently 
the yellow slime extends upward into the bundles of other scales and sidewise slowly into 
the parenchyma, until finally the bulb is destroyed. In the later stages of the disease 
small pockets occur in the bulb-scales (plate 20, figs. 8, 9) and other bacteria frequently 
enter and help to complete the destruction of the bulbs but their presence is not essential. 
: In this stage, mites (Rhizoglyphus 
hyacinthi) may also be present 
(plate 20, fig. 7). Certain fungi 
are also met with in later stages, 
and notably a species of Penzcil- 
lium. This is extremely common 
(plate 20, fig. 11). Wakker states 
that there may be also an up- 
striping of the green leaves due 
to their infection from the bulb. 
The above signs progress very 
slowly, several months to a year 
being necessary, as a rule, for the 
complete destruction of the bulbs. 
Not infrequently the disease ex- 
tends from the mother-bulb, by 
way of the plateau, into daughter- 
bulbs (Wakker, Smith). In such 
cases the daughter-bulb always 
shows the disease first in the basal 
portion (plateau), and of course, 
on the side next to the mother- 
bulb. Bulbs are frequently at- 
tacked on one side more than on 
the other (plate 19, fig. 9), and this may result in a curved growth of the foliage which 
bends over toward the diseased side. 
ETIOLOGY. 
The cause of this disease is Bacterium hyacinthi Wakker; a bright-yellow, medium- 
sized rod with rounded ends, motile by means of one polar flagellum, and multiplying by 
fission. It is this organism which causes the yellow color in the bundles of the diseased 
bulbs. The yellow slime in the bulbs is made up entirely of a homogeneous-looking bac- 
terial growth which in early stages ordinarily yields pure cultures of this organism when 
cultivated out with any degree of care, but which is sometimes mixed with other organisms, 
especially in advanced stages of the disease. Wakker, who first studied this disease criti- 
cally, obtained at different times a number of good cases as the result of wounds made in the 
leaves, scapes and bulbs, but inasmuch as most of his successful inoculations were what the 
writer has designated direct infections, i.e., the inoculation of raw material, there has been 
a tendency on the part of various writers to discount his results, and to confuse the general 
reader by speculations not based on any experimental data. Dr. Wakker’s statements are, 
however, in the main, trustworthy, since the writer has obtained numerous successful con- 
firmatory inoculations from pure cultures of this yellow organism (for figures consult 
Bulletin 26). 
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Fig. 131.* 
*Fic. 131.—Early stage in the destruction of a hyacinth bulb by Bact. hyacinthi. Cross-section of bulb enlarged 
to’show diseased vascular bundles in 3 scales. These 6 bundles were bright yellow. A seventh bundle, which does 
* not show plainly in the cut, was also diseased. Several of the dark spots are negligible, being shadows due to slight 
openings between the scales. Plant inoculated Feb. 16, 1897, on upper part of scape. Photographed June 23, 
1897. Circa x 3. 
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