ANTHRACNOSE OF CUCURBITS. 



51 



ATTEMPTS TO PROVE THE PRESENCE OF THE FUNGUS ON THE SEED. 



With all of the observational evidence pointing so strongly toward 

 seed carriage of the fungus, repeated efforts were made during the 

 spring of 1917 to isolate the organism from commercial seed or in 

 other ways to prove its presence. 



Besides numerous samples of seed collected at the Ohio farm 

 at different stages in the cleaning process, a generous supply of 1916 

 seed was later secured from that farm. This seed, as well as some 

 of that used in 1916, was tested in a variety of ways in an -attempt 

 to detect the presence of the anthracnose fungus. The following 

 methods were employed: 



(1) Seeds were placed in agar plates. 



(2) Seeds were planted in Petri dishes on sterile filter paper moistened with water 

 or a nutrient solution. 



(3) Seeds were planted in large damp chambers on moistened filter paper. 



(4) Seeds were planted in sterile sand in damp chambers. 



(5) Seeds were planted in sterile soil in flats in the greenhouse. 



In the first three methods the fungus might be detected by its 

 saprophytic growth on the substratum or by its parasitic develop- 

 ment on the seedling. In the last two methods the latter possibility 

 was relied upon. The results of these tests are summarized in 

 Table V. 



Table V. — Summary of laboratory tests of cucumber and muslcmelon seeds to prove the 

 presence of the anthracnose fungus. 



Date. 



Seed used. 





Source. 



Number. 



1910. 

 Aug. 28 



1917 

 Feb. 5 



Iowa, 1915.. 



Ohio 



( l ) 



15 

 15 

 24 



8 



30 



200 



33 



1,200 

 150 

 150 



200 



48 



6 



12 



6 



6 



12 



100 



100 



100 



100 



1, 100 



400 



60 



5 





5 

 5 



Ohio (fruit tissue adhering) . . . 

 Ohio 



5 

 26 



Ohio (fruit tissue adhering) . . . 

 Ohio 



26 

 Mar. 3 



Ohio (fruit tissue adhering) . . . 

 Ohio 



12 



12 



13 

 14 



do 



Ohio, collected in October, 

 1916. 



do 



do 



23 



Ohio 



23 



do 



23 





23 



do 



23 



do 



23 



Ohio 



24 





27 



do 



27 

 27 



Ohio, collected in 'October, 



1916. 

 Ohio 



27 



do 



May 1 



Ohio (fruit fragments adher- 

 ing). 



Total 





4, 069 



Method. 



Time 



in 

 days. 



11 dilution plates in 2 per cent dextrose 

 agar from wash water. 



5 in each of 3 plates, 2 per cent dextrose agar . 

 do 



6 in each of 3 plates, 2 per cent dextrose 

 solution in filter paper. 



Same, in plate 



6 seeds in each plate ; filter paper plus water . 



Wash water on cucumber plants 



In drops of water on cucumber foliage; 2 

 plants. 



12 sterilized sand flats, in greenhouse 



Damp chamber, wet filter paper 



.....do 



Sterile sand, in damp chamber 



2 per cent dextrose solution, in filter paper. 



Wet filter paper 



Prune decoction, in filter paper 



2 per cent dextrose solution, in filter paper. . 



Wet filter paper 



Prune decoction, in filter paper 



Wet filter paper, in damp chamber 



do 



Sterile sand, in flat 



do 



do 



Sterile loam, in flat 



Sterile sand, in damp chamber . 



( 2 ) 



Two pounds. 



2 Failure. 



