8 



Journal of Agricultural Research 



Vol. IV. No. I 



placed in glass moist chambers. Transfers from a spore suspension of 

 the Phoma fungus were made with a camel's-hair brush to the blossom 

 end, the stem end, and the sides of the fruit, after which some of the 

 tomatoes were needle-pricked, while care was taken not to wound the 

 others. Check tomatoes not treated with the spore suspension but kept 

 in moist chambers under similar conditions were used as controls. Four 

 days after inoculation a darkening of the tissue became visible about 

 the pricks, especially at the stem end of the tomatoes. Where there had 

 been no wounding of the tissue, no discoloration appeared. Ten days 

 after inoculation diseased areas 2 to 3 cm. in diameter had developed 

 from needle-prick inoculations on the sides and at the stem end of the 

 tomatoes. The dark tissue in the central part of the spots was sur- 

 rounded by a watery-looking zone. Cracking of the discolored tissue 

 had occurred in some cases, and within the cracks a grayish white 

 mycelium could be seen. On tomatoes not wounded at the time of 

 inoculation (and not cracking later) no discoloration appeared. There 

 was, however, in some of the nonpricked tomatoes a cracking of the 

 tissues at the stem end, and in these cases the typical discoloration due 

 to the presence of the fungus was observed. 



A final examination made at the end of three weeks showed well- 

 developed diseased spots about needle-prick inoculations, while no spot- 

 ting occurred upon uninjured tomatoes treated with the fungus, except 

 where natural spUtting of the tissue at the stem end allowed the fungus 

 to enter. The check tomatoes showed no evidence of disease. Several 

 of the needle-pricked tomatoes kept in the moist chamber and showing 

 spots at the stem end of the fruit were selected and photographed. 

 (PI. A, figs. 2, 3, 4, and 5.) Freezing microtome sections were made 

 from tissue taken from fruit spots and the development of pycnidia and 

 pycnospores was studied. Plate I, figure 6, shows the structure of a 

 pycnidium in cross section. Within the darker outer cells are several 

 layers of hyaUne cells from which arise the basidia bearing the spores. 

 In Plate I, figure 3, a few of these spores are shown under higher mag- 

 nification. Table III gives the results of these inoculations. 



Table III. — Results of the inoculation of green and ripe tomato fruit with Phoma fungus 



{laboratory experiment) 



