Apr. IS, 191S Phoma Destructiva 



Control plants placed beneath bell jars and subjected to the same condi- 

 tions of humidity and temperature as plants used in this and the former 

 experiment gave no evidence of disease. Since young tomato plants 

 had proved susceptible to infection of the fungus under conditions of high 

 temperature and humidity, it was decided to subject mature tomato 

 plants to a similar test. Accordingly two nearly mature tomato plants 

 (90 to 100 cm. high) growing in pots and bearing green fruit were selected 

 and placed in glass infection cages.^ One of these plants was thoroughly 

 sprayed (January 17, 1914) with a spore suspension of the fungus, made 

 by adding distilled water to a lo-day-old corn-meal culture. Spraying 

 was done with a small atomizer, the foliage, stem, and fruit being thor- 

 oughly wet with the solution. The other plant was placed in a similar 

 cage and sprayed with sterile water. In four days small dark spots had 

 appeared on the foliage of the inoculated plant, giving the lower leaves 

 a speckled appearance. A diseased leaf was picked, brought to the 

 laboratory, and examined. It was found that each dark spot repre- 

 sented a point of fungus infection, as many as 50 spots being counted 

 on a single leaflet. By means of beef -agar plates pure cultures of the 

 Phoma fungus were recovered from this diseased leaf tissue. Infection 

 spread rapidly upon the plant in the cage, until in 10 days' time the 

 whole plant was badly spotted. Six of the lowest leaves had fallen 

 from the stem, while those a little higher up were discolored, shriveled, 

 and drooping. The upper leaves which were still green showed dark, 

 irregular spots. Upon some of the petioles dark streaks and blotches 

 occurred. On January 27, 1914 (10 days after inoculation), a photo- 

 graph was made of the diseased plant taken from the infection cage 

 (Pi. II, fig. 2). The control plant which showed no spotting or falling 

 away of leaves was also photographed (PI. II, fig. i). Some of the 

 tissue from the diseased plant was again examined in the laboratory, 

 and plate cultures were made. Out of tissue cut from leaf spots pure 

 cultures were isolated. A few of the leaves which had fallen from the 

 inoculated plant were photographed separately in order to show more 

 clearly the character of the spotting (PI. IV). Three weeks after inocu- 

 lation green and partly ripened fruit growing upon this diseased plant 

 showed no signs of disease. 



INFECTION OF GREEN AND RIPE FRUIT IN THE LABORATORY 



In addition to the greenhouse experiments some infection tests were 

 carried on in the laboratory. Green and ripening tomatoes were picked 

 from healthy plants growing in the greenhouse. This fruit was washed, 

 soaked in mercuric-chlorid solution (i to 1,000) for 30 minutes, and 



■ The infection cages used had glass tops and sides set in wooden frames. When placed over the inocu- 

 lated plants, the whole cage was raised about s cm. by means of supports, in order to allow ventilation. 

 Capacity of cage, 170,633 c. c. 



