the result that parasitic organisms may be influenced in artificial cultures 

 by the nutritive medium used. In this their virulence is proved always to 

 be less than it is under natural conditions. By leeching the cultures, fluids 

 may be obtained which may be used for the immunization of the host plants 

 against the organism concerned. The author concludes further that the in- 

 fected plants are actually cultures of the parasites concerned. In this 

 maceration and extraction of the diseased plant jjarts must furnish fluids 

 which would exercise an effect similar to that of the |)arasite itself. \\'hon 

 modified by increased temperature, these fluids can 1)C used for immunization. 



E. MarchaP should be especially mentioned as a representatixe 

 of the other line of immunization experiments. He worked with mineral 

 substances, some of which were nutritive, while others should be considered 

 poisonous. He sowed lettuce in Sachs' nutrient solution with the addition 

 of substances which kill fungi. The young seedlings, after the development 

 of the first two or three leaves, were infected with the zoo-conidia of Brcmia 

 Lactucac and then kept in a moist atmosphere. The plants, not rendered 

 immune by the substances in the nutrient solution whicli would kill fungi, 

 were at once attacked. Of the salts used, the addition of irom three to four 

 ten-thousandths copper sulfate to the nutrient solution was clearly proved to 

 increase the resistance. The addition of i-ioooo copper sulfate no longer 

 showed any immunizing effect whatever. ^Manganese sulfate acted less com- 

 pletely ; ferrous sulfate had no effect at all. Calcium salts also (up to 2-100) 

 could increase the resistance while nitrates and also, curiously enough, phos- 

 phates lessened it. 



The idea of increasing each individual's susceptibility to vegetable para- 

 sites by changing the cell sap through the addition of foreign substances was 

 also taken up by zoologists who proceded in accordance with the discovery 

 that parasitic animals, for instance, scale, seek out weakened plants especially. 



Now, however, was associated with this the though i that universal con- 

 ditions of weakness in cases of constitutional disease as well as conditions of 

 susceptibility to parasitic attack could be healed by supplying salts of some 

 definite kind to the plant body extra-radically. This taking up of substances 

 otherwise than through the roots was called "Internal Therapy' and was 

 developed methodically. 



In 1894, I. Schewyrjov- published an article on "the impregna- 

 tion of the wood in living trees with solutions of coloring matter" (Ueber die 

 Durchtrankung des Holzes lebender Baume mit Farbstofflosungen"). In 

 ii he describes the apparatus which he constructed for this purpose which we 

 will call nutrition tube and nutrition basin. The tube is of steel, pointed at 

 one end, which is driven into the bark, while the other end is closed by a 

 cork, through which passes a gimlet. The tube is filled with the experimental 

 liquid, through special openings, by means of a rubber tube. Then the gimlet 



1 Marchal, E. De rimmunisation de la laituc centre le meunier. Compt. rend. 



1902. CXXXV, p. 1067. 



-' Schewyrjov Iwan, Berichtigung- usw. Zeitschrift ftir T^flanzenkrankhciten. 



1904. p. 70. 



