Ge sated 
29 
ting. ‘The leaf was exposed to direct sunshine during the greater part of 
the time: 
| Interval, 
| Lossof | Loss per 
weight. minute. 
come sees | OMe | a 
Minutes. | Gram. | Gram. 
6 0.15 0, 025 
18 | 17 | .018 
50 . 26 . 005 
310 .70 002 | 
| a | J 
The average loss per minute during the last interval was only 8 per 
cent of that during the first. Transpiration does not usually cease so 
promptly, and the relative loss is less, the longer the first period is made. 
It is a general rule, in experiments of this kind, to permit the subject to 
stand for a time after cutting, and thus to become accustomed to its new 
conditions before observations really begin. If this is done with Cocos 
the rapid initial transpiration can not be observed, and thus the abnor- 
mality of the results obtained must escape suspicion. Many of my tables, 
which seemed satisfactory when made, are valueless on this account. 
When the transpiration of a leaf varies during a single half day by 92 per 
cent of its maximum activity, independently of any change in the environ- 
ment, it is obvious that any modification of the latter must have results 
which are comparatively too insignificant to be studied with any con- 
fidence. Therefore, I was forced to seek a means of preventing the usual 
reaction to the cutting of the pinne. 
The water in which cut pinne stand ceases to be clear, becoming a pale, 
often opalescent, brown. This is sometimes evident within half a day 
after cutting, but usually it is not seen until a day or more has elapsed.?® 
Suspecting that an exudation from the cut surface (though none was 
visible) might be preventing the absorption of water, I tried renewing the 
cut. It was doubtful if the transpiration was accelerated ; certainly such 
acceleration was not enough to be applicable in drawing any conclusions. 
It was shown by Janse ” that, while boiling a part of the path of the 
transpiration stream ultimately results in interference with the movement 
of water, this result is not immediate, and is due to changes in the part 
remaining alive, not in that killed. It occurred to me that boiling the 
bases of the pinne might prevent the checking of their absorption for at 
least a few days. As a matter of fact, the cessation was less immediate 
and less complete in pinne so treated than in others, but it was still so 
great that the results obtained by this method alone are far from satisfac- 
tory. They are shown in the next table. 
"This is a conspicuous exception to Sachs’s statement that nothing escapes from 
such cut surfaces into water. 
” Janse, J. M.: Die Mitwirkung der Markstrahlen bei der Wasserbewegung im 
Holz, Jahrb. wiss. Bot. (1887), 8, 1. 
