MR. A. J. EWART ON ASSIMILATORY INHIBITION. 459 
light and in darkness at different stages of their development by 
certain of the leaves previously examined. The CO, is absorbed 
by potash, and the deerease in the volume of the receiver gives 
CO, 1 
the amount of CO, evolved, assuming that Q. =i is the 
2 
respiratory quotient. 
Corylus Avellana.—Temperature 25? C. 5 grammes in A, B, and C. | 
Ay Young apices, Largest leaf, L. Ys, evolved of CO, in 34 hours 
[ stipules removed. in bright light 13:1 c.c., in darkness 13°9 c.c. | 
B. Leaves, L. š, B. y, evolved of CO, in 3} hours in bright light 6:1 c.c., | 
in darkness 127 c.c. | 
C. Leaves, L. }, B. +, evolved of CO, in 34 hours in bright light 0-2 c.c., 
in darkness 8:1 c.c. ü 
Phaseolus vulgaris. 
D. 20 leaves, L. à, leaflets L. ç, B. 5, and partly expanded, evolved of 
CO, in 3 hours in bright light 1:9 c.c., in darkness 2 c.c. 
E. 10 leaves, L. y, leaflets L. }, B. 1, fully expanded, evolved of CO, in 
3 hours in bright light 0:3 c.c., in darkness 25 c.c. 
In C and E, although assimilation is stronger than respiration, 
a small quantity of CO, is given off on exposure to light. This 
is due to the escape and absorption of traces of respiratory CO,, 
which when once absorbed are no longer available for assimila- 
tion, and the same phenomenon is shown by actively assimilating 
leaves when exposed to bright light. In A, C, D,and E the 
results coineide with those obtained by the Bacterium method ; 
but in B respiration is apparently twice as active as assimilation, 
although by the Bacterium method a moderately active evolution 
of oxygen, which is in parts weak, is shown. — Thisis because the 
leaves are at this stage folded and quite hairy, and are hence 
under less favourable conditions for assimilating and evolving 
oxygen than when examined in the form of sections under 
optimal illumination by the Bacterium method. ^ Although, 
theoretically, gas analytical methods should, since they permit 
the error due to respiration to be allowed for, which is impossible 
by the Bacterium method, form a more certain test for the 
presence or absence of the power of assimilation than the latter, 
as a matter of practice, the Bacterium method is, largely owing 
to its microscopical and more specialized application, a much 
more delicate and certain detective agency. 
LINN. JOURN.—BOTANY, VOL. XXXI. 2k 
