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Rh seen in the middle record of Fig. 681), where the rate is seen to be double the normal. Continued action, however, caused a depression: the third record of this series shows this, where the reduction is three-fourths of the normal rate.

Ether : ereriment 64.——In Fig. 680, the records exhibit the effect of introduction of ether vapour into the plan! chamber, and its recovery after the removal of the vapour. Ether is seen to depress the rate of growth to a little more than a third of the normal rate. The recovery is seen to be. nearly complete half an hour after the removal of the vapour.

Carbonic Arid.- preriment (Li—The action of this gas is very remarkable. The plant was immersed in water and normal record taken; the plant chamber was now ﬁlled with water, charged with carbonic acid gas. This induced a very marked acceleration of growth (Fig. 69). In a Slut- ling of nion, the increase was found to be two and a half times. In the ﬂower bud of (Irmum, the rate was found enhanced threefold from the. normal 0'25 ,1. to 0'75 [a per second. After this preliminary enhancement, there was a de- pression of growth within 15 minutes of the application, the

FIG. GEL—Effect of Co._.. (a) Normal mount: (6) immediately after application of CO. and (c) 1:3 minutes after.