342 BACTERIA IN RELATION TO PLANT DISEASES 
The new varieties are also cataloged by one of the growers, and of these 7 are marked 
“as much subject and 6 as very resistant, while 31 do not fall into either class. 
Wakker states that most of the leaf-infections are usually observed in the fields in the 
month of May, but thinks that infection must take place at least a month earlier. The 
writer’s experiments have led him to the same conclusion. Undoubtedly the bulk of the 
field infections occurs during blooming time, when insects would be visiting the blossoms 
freely. 
The downward movement of the disease in the leaves is very slow (Wakker, Smith). 
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Fig. 134.* 
MORBID ANATOMY. 
There are no hyperplasias in connection with this disease. It is primarily, and to a 
considerable extent during its whole progress, a disease of the vascular bundles. The 
reasons for this the writer has attempted to set forth in his papers on this organism (see 
Literature). They are noted briefly under the next head. The xylem portion of the bundle 
is the first part to be attacked, especially the spiral vessels which are soon filled entirely 
by the rapid multiplicatidn of the organism (plate 20, fig.6). This is what causes the bright 
*Fic. 134.—Cross-section of base of a hyacinth bulb, showing cavities in parenchyma due to Bact, hyacinthi. 
Upper part of drawing is extreme base of a bulb scale; lower is part of plateau. Starch grains are represented in 
. outline only. Slide 502 A—A3, from plant No. 67 inoculated in the flowers (see Bull. 26, p. 30). 
*Fic. 135.—Bact. hyacinthi: A detail from fig. 134 at X. 
