4 BULLETIN 1029, U. S. DEPARTMENT OF AGRICULTURE. 



Histological studies to trace the course of the mycelium within 

 and beneath the seed coat have not been made. It became evident, 

 however, as a result of cultural studies, that the effect on diseased 

 seeds may vary from little or no change in normal color and little 

 shriveling to very marked shrinkage and entire loss of vitality, de- 

 pendent upon the extent of invasion by the fungus. That the infec- 

 tion may be confined to the seed coat is shown by one instance where 

 a seed which had been treated with 1 : 1,000 mercuric chlorid to kill 

 organisms on the surface was placed on a potato-agar plate. Normal 

 germination occurred and the hypocotyl as it developed became 

 attached to the agar about half an inch away from the seed coat. 

 As growth proceeded the young seedling was drawn entirely away 

 from contact with the testa and was later removed to a tube of agar, 

 where it remained sterile. Subsequently, however, a pure culture of 

 Phoma lingam developed from the seed coat, proving that the fungus 

 was present in this portion of the seed without having invaded the 

 cotyledons. 



In the study of the effect of fungicides upon germination and 

 subsequent development of seedlings from normal cabbage seed, most 

 of the work was done with two lots (Nos. 2-18 and 3-18) of the 

 Wisconsin Hollander variety grown at Racine, Wis., in 1918. In 

 general, one lot (No. 2-18) showed more injury from disinfectants 

 than the other, in spite of the fact that a high percentage of the 

 untreated seeds germinated and produced vigorous seedlings. This 

 may have been due to improper curing, since the seed plants after 

 being harvested were piled indoors before the seed was thrashed and 

 the circulation of air provided was insufficient for rapid and thor- 

 ough curing. A portion of lot No. 2-18 was stored in a cloth sack 

 in the laboratory, and certain of the treatments were repeated in the 

 second year (winter of 1919-20). After the general limits of injury 

 with these two lots of seed had been determined, the effect of stronger 

 treatments was usually extended to several other lots of various ages 

 and from different sources. 



In a few of the early experiments germination tests were made in 

 Petri dishes lined with moistened filter paper. It was found that 

 numerous treated seeds often gave evidence of germination by throw- 

 ing off the testa and starting growth of the hypocotyl, but develop- 

 ment ceased at this point. When parallel tests were made in soil in 

 the greenhouse, most of such seedlings never appeared above ground. 

 Consequently, in order to secure a more definite index of the capacity 

 of various lots of seed for producing vigorous seedlings after treat- 

 ment, the Petri dish method was discarded. All results reported on 

 the effect of fungicides upon commercial seeds are from tests made 

 in silt-loam soil in the greenhouse. The final estimate of the amount 

 of injury was supplemented in the case of the stronger treatments 



