[Vol. C 



148 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



ferently and in some cases with a different germicide. This 

 is perhaps only what is to be expected when one realizes that 

 various soil bacteria and fungi show a wide range of tolerance 

 towards the same toxic agent. A good example of this is cited 

 by Makemson ('17) in his work with Cladosporium fulvum. 

 He found that the spores of this fungus would germinate in a 

 relatively strong solution of Bordeaux mixture in a hanging- 

 drop culture. He noted further that under the conditions just 

 mentioned the germ tubes grew as rapidly as in the control. 

 On the other hand, the toxicity of Bordeaux mixture for most 

 fungi is well known. 



Many species of Fusarium are able to grow in a 1 per cent 

 copper sulphate solution. Young and Cooper ('17), in their 

 work on the determination of fungicidal coefficients, found that 

 Endothia parasitica was killed at a dilution of 1 to 16,000 com- 

 mercial lime-sulphur solution, while it required a 2 per cent 

 solution of copper sulphate to kill this organism, both fungi- 

 cides acting for a period of 15 minutes. On the other hand, 

 when Glomerella cingulata was used and the same time in- 

 terval employed, a dilution of 1 to 9600 commercial lime-sul- 

 phur was necessary to kill the spores, while a 1 per cent solu- 

 tion of copper sulphate was lethal. Lime-sulphur, therefore, 

 is almost twice as toxic to the spores of Endothia parasitica 

 as to those of Glomerella cingulata. The reverse is true in 

 the case of copper sulphate. Horn ('04) found, in his work 

 with some of the Pliy corny cetes, that exceedingly small traces 

 of CuS04 would prevent growth. The success of the fungi- 

 cide, then, must depend upon the species of bacteria or fungus 

 present on the seed. 



The nature of the seed will affect the selection of a germi- 

 cide, since the resistance of different seed is as variable as 

 that of spores. With respect to different germicides it is 

 known that seeds may exhibit marked differences in permea- 

 bility. The moisture content of the seed will also probably 

 modify its resistance to any injurious agent. This fact has 

 been frequently pointed out, and recently clearly demonstrated 

 by Coons and McKinney ('17) in their work on the treatment 



