6 Journal of Agricultural Research voi. iv, no. i 



In tomatoes diseased by inoculation with the Phoma fungus the dis- 

 coloration was found to penetrate from 2 to 3 cm. into the interior of the 

 fruit, and microscopic examination showed an abundance of hyaline to 

 brownish mycelium in the watery-looking tissue, as well as in that of the 

 darker central tissue. 



INFECTION OF TOMATO FOLIAGE; IN THE GREENHOUSE 



As already mentioned in connection with the inoculation of tomato 

 fruit, the Phoma fungus was also inoculated into both stem and leaf 

 tissue of young and mature tomato plants growing in the greenhouse. 

 In a few instances a slight discoloration had been noticed, but no definite 

 spotting had been produced. Up to this time no effort had been made 

 to subject the inoculated plants to a higher temperature or to a more 

 humid atmosphere than that afforded by ordinary greenhouse conditions. 

 In January, 1914, a series of experiments was begun in the greenhouse 

 to determine whether or not leaf infection would occur in plants placed 

 under conditions more favorable to the development of the fungus. 



Healthy young tomato plants of the Earliana variety growing in pots 

 in the greenhouse were used. When inoculated, the plants were from 

 10 to 15 cm. in height. A spore suspension of the Phoma fungus, made 

 by adding sterile water to a corn-meal culture containing an abundance 

 of mature pycnidia, was transferred by means of a platinum loop to the 

 leaf surface. The tissue was then needle-pricked and the plants placed 

 under glass bell jars. Control plants were used. The atmosphere 

 beneath the jars soon became saturated, and drops of water collected on 

 the inside of the jar and upon the surface of the plant. In three to 

 five days a discoloration of the leaf tissue was noticed about the points 

 of inoculation, and in eight days definite dark spots had developed. 

 These spots varied in size from 2 to 10 mm. In some cases several spots 

 had coalesced, spreading across the entire leaflet. Photographs were 

 made of two of these diseased plants (PI. II, figs. 3 and 4). A micro- 

 scopical examination of tissue taken from these spots showed the myce- 

 lium, pycnidia, and spores of the Phoma. From diseased tissue cut from 

 some of the spots agar plates were poured and the fungus reisolated in 

 pure culture. 



A second experiment with young tomato plants was tried, the 

 inoculation being made by spraying with a spore suspension. No 

 needle pricks were made. The plants were placed beneath glass bell 

 jars in the greenhouse, and within five days dark spots had developed 

 (PI. B, figs. 2 and 3). Small drops of water were noticed on the plants, 

 especially along the edges of the leaves. Frequently the infection 

 started beneath these drops of water, the discoloration spreading from 

 the edge of the leaf inward. Microscopical examination of tissue from 

 the diseased areas showed mycelium and pycnidia of the Phoma fungus. 



