354 Dr. E. Drabble and Miss H. Lake. [May 12, 
In order to record the curvatures observed, the following notation is 
adopted. The least appreciable curvature is denoted by b—;. 6, 6+, and 
b+ +, being used to express successively greater degrees of curvature. By 
-reading against squared paper it has been found possible very accurately to 
allot values to these letters. If b— be equivalent to a value 3, then 0 is 4, 
b+ is 5, and 6++ is 7. By employing the values thus obtained, a curve 
eraphically expressing our results with different partial pressures has been 
plotted. 

Curve showing Amount of Curvature in different Partial Pressures of Carbon Dioxide. 
Ordinates express curvature and abscisse percentages of carbon dioxide. 
Serves A.—Mixtures employed: Air; 1 per cent. COz in air; 10 per cent. 
COz in air. The response in air was more rapid than in 10 per cent. COz, 
but distinctly less rapid than in 1 per cent. COs (see Table I). 
Serves B—Mixtures employed: Air; 3 per cent. COz in air; 74 per cent. 
COz in air. Curvature was effected slightly more quickly in 3 per cent. COz 
than in air, while but little difference could be observed between the plants 
in air and in 74 per cent. COs (see Table IT). 
Serves C—Mixtures employed: Air; 1 per cent. COgin air; 3 per cent. CO, 
in air. The curvature was first apparent in 1 per cent., while in 3 per cent. 
it appeared earlier than in air (see Table III). 
Series D—Mixtures employed: Air free from CO.; Air; 2 per cent. 
COs. Curvature first set in in 2 per cent. COs, that in air being more 
marked than in air free from CO» (see Table IV). 
Serves H—Mixtures employed: 1 per cent. COz; 2 per cent. COs. The 
first bending occurred in 1 per cent. COz (see Table V). 
Serves F.—Mixtures employed: 0-2 per cent. CO2; 0°5 per cent. COs; 
1 per cent. COz, The earlier bendings were most vigorous in 1 per cent., 
