85 
In May some leaves of Antigonon leptopus were cut off 
together with the long branch and placed in the dark. After 
22 hours the loss was 0.23 gr. an hour. Leaves taken from the 
plant at 4 p. m. and placed in the dark, were found to have 
lost 0.22 gr., also per hour. Although the figures 0.23 and 0.22 
an hour for each M’ do not exactly express the nightly loss, 
it is obvious that the real numbers cannot differ much from 
these. And notwithstanding the slight loss Antigonon leptopus 
with its rich racemes of red flowers, with which almost all 
the year round it covers walls and treetrunks, is a plant that 
must have great quantities of organic food at its disposal. 
Doubt was expressed a few lines higher up, whether the 
temperature really plays so important and exclusive a part as 
is generally assumed. That its influence is great, appears from 
Sachs’s experiments, though this author himself also cites some 
instances of plants which in a cool night had lost their rich 
store of amylum. 
Various facts make me incline to believe that the light as 
such has some influence. In the first place the behaviour of 
Coca leaves with regard to the iodine experiment. As is well- 
known, the leaves of Erythroxylon Coca, var. Spruceanum 
Bck.") have an apparent vein half way between margin and 
midrib. This pseudo-vein which simply points out the place 
where the blade was folded in the bud, divides each lateral 
half of the leaf pretty exactly into two equal parts. The fol- 
lowing list gives the changes of colour, which Coca leaves cut 
off at different times showed when tested with iodine. 
{ inside the pseudo-vein light blue 
6 a. m. 
ee | outside , ‘ » almost colourless 
insi lighter blue 
i, MIRIGE og? ay o di 
ote outside , ‘ , colourless 
e 103 inside, * , Slightly lighter than in a 
ae Pane Fe ; , hereand there a little blue 
1) Observations on the plants known by the name of Erythroxylon Coca as 
cultivated in the East Indies. By Dr. W. Burck (Tejjsmannia, Batavia 1890). The 
paper is in Dutch. 
