INTUMESCENCES . 



139 



The results of these experiments seem to indicate that 

 the formation of the intumescences on the cauliflower leaves 

 might have been due to either the copper or the ammonia 

 in the ammonium copper carbonate solution. The ammo- 

 nium carbonate solution was selected for the experiments 

 because ammonium carbonate gives off ammonia very 

 slowly when exposed to the air. The experiment just de- 

 scribed was repeated several times, using the ammonia in 

 various concentrations, and ammonium carbonate, and 

 in nearly every instance eruptions of a characteristic 

 form were produced. In applying the spray to the 

 leaves, a glass atomizer was used in which the copper 

 solutions had likewise been placed for the first tests. 



Although 



several days had elapsed since 



using 



the 



copper solutions in the atomizer and although it was thor- 

 oughly cleaned and washed, it was thought barely poss- 

 ible that some copper might have been retained by the 

 walls of the glass vessel, as described by Nageli 15 . On 

 that account the tests were repeated, using ammonia and 

 ammonium carbonate, and this time the sprays were applied 

 to the leaves by means of brushes, so that all chances for 

 the possible contamination with copper were avoided. In 

 this last series of experiments all of the plants sprayed with 

 ammonium copper carbonate, two of the plants sprayed 

 with ammonium carbonate and two of the plants sprayed 

 with 2% ammonia developed intumescences. Two of the 

 plants sprayed with 2 % ammonia showed only discolored 

 spots. Of the plants sprayed with ammonium carbon- 

 ate, one only showed discolored spots. While several 

 of the sprayed spots undoubtedly formed intumescences 

 as a result of spraying with ammonium carbonate or 

 ammonia, owing to the negative results of several plants 



it will not be possible without further tests to definitely 

 ascribe the formation of these intumescences to the am- 

 monia. 



At the same time that the cauliflower leaves were 





