82 
The cause or at least one of the causes why trees and tall : 
shrubs are falling off after twelve, is evident; indeed, from 
herbs it is possible to cut off leaves that during the whole day 
are exposed to the sunlight, whereas this is impossible with : 
taller plants. The leaves within easy reach are either in the 
sunshine before 12 and in the shade afterwards, or vice versa, 
That this circumstance produces a great difference became 
evident from an observation on Connarus falcatus, the shrab- 
already referred to, pretty big-sized and much too tall to allow — 
of its highest leaves being cut off without using a ladder. At 
6.15 a. m. a few leaflets were cut off, which looking eastward 
after a short time would have been struck by the sun’s rays — 
and remained exposed to them down to 12 o’clock. The day | 
was June 1*; the sun being consequently, in the North and © 
unable to reach the leaf a few minutes after twelve, since it © 
soon got into the shadow of other leaves. Not till 3.50 p. m | 
the opposite leaflets were cut off to be compared with those | 
of the early morning. Weighing and calculation showed that 1 
the gain was only 0.10 gr. an hour for each square Meter. On 
the same day and at the same hours the converse experiment 
was made, that is to say, at 6.15 a.m. some leaflets from the 
Westside were taken, and the opposite ones at 3.50 p. m.; the 
latter having enjoyed the direct sunlight after 12 o'clock. AS 
to these it appeared that they had produced 0.32 gr. an hour, 
consequently three times the amount of the former leaflets. | 
A few days before on a brighter day than the first of Jum) 
the production of leaflets exposed to the sunlight after 12 rose | 
to 0.44 gr., whereas under the same circumstances leaflets which | 
had been shone upon till twelve only, even suffered a loss 
0.09 gr. an hour. The latter were consequently lighter in 
afternoon than in the morning. This affords an explanation 
the fact that Connarus falcatus , examined on May 21 betw 
2.10 p. m. and 5.25 p. m. showed loss, whereas Connarus B¥ 
crophyllus on the same day and during the same time hi® 
Increased the store of its leaves. Although in these case” 
omitted to record from which side the leaves had been taker 
