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Prom nut the root, infeetion is possible even with plants of two 

 or more decimeters in height. If for this purpose woundings of the 

 root aie necessary, is not yet clear; probably roots may absorb the 

 virus from the ground even througli their unhurt surface. As infec- 

 tion only occurs in the buds and meristems, the number of healthy 

 leaves found at tlie bottom of the pUmt, indicates in some way the 

 date of the infection, in case the virus lias entered through the root 



Without any loss of virulence the virus may be dried andintlia. 

 state exist through the winter, for instance in the ground ; part, 

 however, gets lost then, just as is the case with many bacteria and yeast 

 species. The leaves, too, keep their virulence when dried, so that 

 the dust of the brittle leaves helps, no doubt, to spread the disease. 

 Precipitating the virus with strong alcohol from its solution and 

 drying the precipitate at 40° C, it remains virulent. 



As was to be expected, the virus in moist state is rendered in- 

 active, not only by boiling temperature, but already at 90° C. The 

 lowest deadly temperature I have not been able to fix; I think it 

 will be found between 70 or 80° C. 



Above I alluded to the formation of characteristic leaf-monstrosi- 

 ties when a large dose of the virus is injected. Another, but rarer 

 effect of artificial infection, is variegation or albinism. Hitherto I 

 obtained this effect in too few plants, than that I should be able 

 to point out how it may be expected with certainty; but I have 

 some hopes that furtlior experiments will enable to produce it 

 at will. 



That albinism, or at least one of the forms in which it appeal's, 

 shows a certain I'clation to the leaf-spot disease, may be allowed 

 already at a superficial view of tlie latter. However, until now, we 

 are obliged to admit that an important difference exists between 

 them as to the way of transferring the infection. In so far as may 

 be concluded from the relatively few experiments concerning this 

 point, infection for albinism requires a direct uniting, by means of 

 grafting or budding of the variegated with the green plant. In- 

 fection, on the contrary, of green plants with the crushed tissue of 

 variegated varieties, seetns never to produce any results. My above 

 mentioned plants, however, indicate thai there must exist another 

 way along which variegation may be called forth, namely by a virus 

 existing outside of the plant. 



Probably there are various other plant-diseases, which originate 

 in a manner alike to that of the spot-disease of the tobacco. The 

 disease of the peach-trees in America, described by Erwin Smith 

 under the name of „Peach Yellows'' and „Peach Rosette" (Ü. S. 



