136 MISSOURI BOTANICAL GARDEN. 



spray 



efo 



the spray with the standard solution of copper ammonium 

 carbonate is capable of producing typical intumescences on 

 plants, such as are usually formed as a result of excessive 

 moisture absorption at a time when the plant is in a con- 





was a 



dition of weakened vitality. The demonstration 

 very striking one because in no case did any of the plants, 

 except the sprayed ones, produce a single intumescence. 

 Both old and young leaves were sprayed and it was found 

 that the young leaves had as a rule produced a larger num- 

 ber of intumescences and bigger ones. The lower surface 

 of the leaves produced larger numbers than did the upper 

 surface. From the result of Dale's experiments 3 , in which 

 it was shown that the intumescences sometimes form under 

 a stoma, it was thought possible that the more frequent 

 occurrence of the intumescences on the lower surface of 

 the leaves of the cauliflower might have some connection 

 with the unequal distribution of the stomata on the upper 

 and lower surface of the leaves. It was found, however, 

 although the number of stomata on the lower side of 

 the leaf is about twice that on the upper side, that the 

 location of the intumescences bore no relation to the 

 position of the stomata. 



Having 



direct result of the application of ammonium copper car- 

 bonate, the next point to be determined was whether the 

 active agent in the formation of the intumescences was the 

 ammonia or the copper. The copper carbonate solution 

 used in the test was made according to the standard method, 

 as follows : 5 oz. copper carbonate, dissolved in a mix- 

 ture of 3 pints ammonia to 50 gallons of water. The solu- 

 tion was found to contain 1.57% ammonia. Some of the 

 solution used in the first experiment was neutralized with 

 hydrochloric acid and this neutral solution was used in 

 spraying a number of plants. In every instance the tissue 

 underlying the spots formed where the solution dried, died 



