THE DUTCH DISEASE OF WALLFLOWER. 



In the summer of 1900, in Holland, van Hall found a disease of the wallflower 

 (Cheiranthus) which was characterized by the constriction of the upper part of the tap root, 

 followed by yellowing of the leaves, which gradually fell off, first the lowest, then those 

 farther up the stem. Cross-sections of the constricted portion of the tap root showed the 

 wood to be brown or black, and the vessels of the wood to be occupied by bacteria, which 

 were traced upward into the branches. Professor Beijerinck proved.it is said, that all of 

 these were one sort. " Infection experiments have not yet been published, so that this 

 disease must be placed with the incompletely known ones." 



Later Briosi and Pavarino published on a similar Italian disease of stock (Matthiola), 

 as described in the following chapter. 



LITERATURE. 



1902. Van Hall, C. J. J. Ziekte der Zomcrviolieren, Cheiranthus animus. In "Beijdragen tot de Kermis der 

 Bakterieele plantenziekten." Academisch Proefschrift, Amsterdam, 1902, p. 72. 



THE ITALIAN DISEASE OF STOCK. 



In 1912 Briosi and Pavarino described a vascular and parenchymatic disease of the 

 common stock (Matthiola annua L-), prevalent in parts of Italy and attributed it to a green- 

 fluorescent bacterium. The following translation gives the substance of their paper: 



Two different species of erueifers are commonly designated by the name " Violaeeiocea:" The 

 Cheiranthus chciri L-, which is the common violaeeiocea, and the Matthiola annua L., commonly 

 called quarantina. 



Of this latter there are some varieties of notable commercial importance, cultivated on a large 

 scale, especially in many sections of the Lignria, where entire fields are covered with them, and 

 furnish abundant and splendid winter flowers for exportation. 



Some years the Matthiola quarantina shows signs of a grave disease, which spreads rapidly and 

 causes such damage in some localities that it is necessary to suspend its cultivation. 



The signs of the disease begin with the appearance on the leaves of spots of a pale green color, 

 of indefinite contour, which at first are observed with difficulty. Following this there appear small 

 brown spots of irregular contour, and more or less punctiform, scattered over the petiole. 



Frequently the leaves, especially the young ones, become more or less deformed, not attaining 

 the normal dimensions, and their margins curl toward the upper surface. 



The inflorescence is arrested in its development and becomes rachitic, and so the flowers lose 

 their commercial value. 



The researches were made on plants gathered by us, in various localities such as Loano [on 

 the Riviera, about halfway from Genoa to Ventimiglia], where some years the disease is active and 

 widespread. 



Morbid anatomy. The disease is not limited to the leaves, but extends to all the organs of the 

 plant : flowers, branches, stalks, and roots. 



Sectioning young branches, it is found that the infection invades first the woody vessels, which 

 show yellowing or browning and are more or less altered. 



The plant forms a zone of corky tissue which twists and circles about the infected vessels, to 

 prevent the spread of the disease in a transverse direction, and limit the diffusion of it in the tissue. 

 Later the disease is able to invade all the wood as far as the pith, which, in some cases, is seen to be 

 strongly corroded. 



In the stalk the infection appears first in the primary wood, from which it extends interiorly 

 toward the pith, and externally toward the secondary wood, as is clearly shown by the yellowing 

 and browning of the walls of the vessels and of the fiber, and by the yellow, brown, or black coagu- 

 lated substance which fills up the lumen of the cells of the diseased tissues. 



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