3° BOTANICAL GAZETTE [JANUARY 
corresponding to the full molecular weight (¢. g., CuSO,.5H,O= © 
249) dissolved in sufficient water to make one liter of solution; 
thus 0.01” CuSO, equals a 0.249 per cent. concentration of the 
crystallized salt. 
In the figures used to illustrate this paper the solid black 
bar indicates that the concentrations used were sufficiently 
strong to kill the spores within twenty-four hours. The square i 
blocks alternating with the open spaces indicates that while — 
the germination of the spores was inhibited, they still retained : 
vitality enough to germinate several per cent. after twenty-four : 
hours immersion. Four parallel lines indicate some germination ~ 
but very poor development. Three parallel lines indicate fair — 
but distinctly abnormal development, and two lines approxi: 
mately normal germination and growth. 
Fig. r shows in a condensed form the results of some four — 
hundred cultures with fifteen fungi in a decoction of sugar beet 
to which had been added copper sulfate. A glance at the . 
page will show that many of the fungi present a really remark- — 
able similarity in resistance to copper. Twelve of the fifteen — 
forms represent a range in lethal concentration of from 0.0099” — 
to 0.0168 x, or slightly less than 70 per cent. variation. This _ 
range of susceptibility may be modified by several important — 
considerations, prominent among which is temperature. All, ] 
except Gloeosporium, were grown at 28° C., a little more or less. 
It is established that a fungus presents its greatest resistance t 
or near its optimum temperature for germination and mycelia 
development. At a higher or lower temperature a smaller 
quantity of the agent results fatally. All the forms used 
except Gloeosporium malicorticus, grew well at 28° C., but it is” 
quite certain that some of them grow better at other tempera . 
tures. Inasmuch as the optimum temperatures for the differ- : 
ent forms were unknown it was thought best to use a uniform — 
®CLARK, J. F.: On the toxic value of mercuric chlorid and its double salts: 
Jour. Phys. Chem. 5: 289-316. 1901; also FLENDE: Ueber Creolin und seine Witk- 
samen Bestandteile. Arch. f. Hyg. sate 
