Report of Cryptogamic Botanist and Plant 



Pathologist. 



The most important investigation of the past year relating to 

 the diseases of plants is that of a very mysterious disease of 

 tomatoes grown in the forcing-house. It was at first supposed 

 that the disease was due to the action of some specific micro- 

 organism, and an extended series of cultural and inoculation- 

 experiments were carried on to determine this question. The 

 results were negative and at the same time indicated that 

 the trouble might be a purely physiological one. Another series 

 of experiments confirmed this view, and it was determined that 

 the trouble was due to the unequal operation of two physiologi- 

 cal processes, i. e., root absorption was in excess of transpiration. 

 This induced an abnormal increase of water in the plant tissues, 

 which could not be gotten rid of by the plant by the ordinary 

 processes, and resulted in the dropsical swelling of the succulent 

 parts just behind the actively growing tissues. The full results 

 of this study were published in Bulletin No. 53 under the cap- 

 tion — " CEdema of the Tomato." 



This oedema or dropsy is probably of greater occurrence than 

 is generally supposed in many plants. During the past summer 

 I investigated a similar trouble of young orchard trees, the 

 result of which is published in the annual bulletin under the title 

 " Oedema of Apple Trees." Another case has also been recently 

 investigated by me in violets grown in forcing-houses. 



Two other articles have been prepared for the annual bulletin, 

 viz., " Powdery Mildew of Crucifers " and "Artificial Cultures of 

 Melanconium fuligineum." 



