230 
BOTANICAL GAZETTE 
[SEPTEMBER 
as for example at A 60, B 40, in fig. 2, we must answer the ques- 
tion: What is the effect of 60 cc. of A+40 cc. of B+100 cc. of water, 
when each salt acts independently of the other ? 
Fic. 2.—Anta 
- ~80 M.M. 
40 
- 20 
Syst a 
; : E 
~ 8 Ss 2 Ab 
onism curve showing growth in 
various mixtures of solutions of the two salts, A 
and nse ithe dilution curves of which are shown in’ 
pS 
Sth ec abscissas 
8. 
represent the number of cc. of the salt solutions 
which are mixed 
with water to make 200 cc. of the 
culture solution in which the plants were grown; 
curves in fig. 1 did 
25 signifies that 75 cc. of solution A 
not 
zontal dotted line; the antagonism at the point C 
E. 
It is obvious that 
we cannot answer this by 
merely adding together 
the abscissas at these 
points on the curves? in 
fig. 1. Since this cannot 
be done, it might be 
thought feasible to ex- 
press the effect of A in 
terms of B, or vice versa. 
If the curves A, A, and 
B, B, in fig. 1 were iden- 
tical, this would be very 
simple, since the additive 
effect of (60 A+4o B) 
would equal the additive 
effect of (60 A+ 4o A) or 
the effect of roo A, which 
is shown by the curve to 
be 11. Proceeding in 
this way, we should find 
the additive effect at any 
point on the antagonism 
curve to be exactly the 
same (that is, 11), and 
the additive effect could 
therefore be represented 
by a straight horizontal 
line, as is done in fig. 2 
(dotted line). 
But when the curves diverge, as in fig. 1, we cannot consider 
the effect of 40 B as equal to that of 40 A; we see by inspection 
3 This is evident, for example, from the fact that the abscissa at 50 on curve AA 
is not equal to exactly twice the abscissa at 100 on curve AA; the abscissa at 30 is not 
equal to exactly twice the abscissa at 60, etc. 
