300 WATTERSON: EFFECT OF CHEMICAL IRRITATION 
In Table III two series are shown, in which glycerine was 
used instead of sugar as the source of the carbohydrate. All of 
the figures here are rather low, owing to the slower growth of 
Sterigmatocystis in such a nutrient medium; the ratios, however, 
bear much the same relation to one another as in the preceding 
series, .61 and.69 (normal) to .77 and .68 (stimulated), respectively. 
In the experiments recorded in Table IV, .082 per cent. (.01078 
normal) FeSO, was used as the stimulant, since this concentration 
is near that which caused the greatest increase in growth in Rich- 
ards’ experiments. A .162 per cent. (.0381 normal) solution of 
LiCl was also tried (Tables V and VI), and although the increase 
in growth was not as great as might have been expected from 
Richards’ results, yet the evolution of CO, bears much the same 
relation to it as in the preceding cases. 
A few experiments were likewise made with Penicillium glau- 
cum. Though Penicilium grows well at a lower temperature 
than does Sterigmatocystis, yet it grows slowly, and the total 
weight of the normal is seldom as great as is that of Sterigma- 
tocystis in the majority of cases. The evolution of CO, is never- 
theless very active, and the number of milligrams of CO, given 
off exceeds that of the dry weight of the fungus. Several of these 
cultures were raised on the usual nutrient medium (Table VI1), 
and one (Table VIII) on a solution in which .5 gr. asparagin re- 
placed the NH,NO, as the source of nitrogen. The weight of the 
irritated fungus in the latter case was much greater than that of 
the normal, but the evolution of CO, kept pace with it to such an 
extent that the ratio is 1.22 as compared with 1.26 in the normal. 
In reviewing, then, the results recorded here, it is evident that 
the addition of small quantities of ZnSO,, FeSO, and LiCl has 
increased the rate of growth of Sterigmatocystis and Penicillium 
so that a larger amount of dry substance is produced within a 
given time than in normal cultures; that at the same time there 
has been an increase in the production of CO,, an increase not too 
great, however, to be accounted for by the enlarged area of the 
plant. The ratio of dry weight to CO, of the irritated fungus is 
therefore approximately equal to that of the normal. Taking into 
account previous results which show that the effect of the addi- 
tion of such poisons is to enable the plant to make more econom- 
