The mornings were as a rule eminently bright; before the 
rain the sky got rapidly covered with clouds. By night it Was 
usually fairly clear. 9 
Method of investigation. After a few preliminary experiments _ 
the following method of proceeding proved to be the most 
effective: the leaves were put into strong alcohol directly after 
being cut off, and with the fluid kept at a temperature of : 
712° C, until they were sufficiently discoloured. The bottles, in 
which the leaves were contained, remained subsequently in the ‘ 
water-bath and were not opened till next morning. The leaves” 
were then put into tall cylindrical bottles, filled with a solu- ; 
tion of hydrate of chloral; in this I followed Schimper’s method — 
and also after his example 5 parts of hydrate of chloral were 
mixed with 3 parts of water’). After remaining a whole day — 
in this liquid, they were immersed into pure water, in order 
to have the hydrate thoroughly washed out. The leaves were 
now quite transparent, with the exception of a few which be : 
came brown. As regards the latter it would have been better 
to treat them with a little hydrochloric acid mixed with the 
aleohol according to the prescription of Hugo de Vries”), but 
the desire to subject all the leaves to the same process, pre 
vented me from altering the original treatment. 
_ After the successive immersions in alcohol, hydrate of chloral 
and water, the leaves were put into a solution of iodine’) 
as used by Sachs ‘). For comparative experiments a large qual 
tity of the solution was prepared and subsequently divided ov 
the leaves to be examined. According to Schimper’s paper cited 
above, this naturalist added the iodine at once to the solution 
of hydrate of chloral, but in my own experiments all the leav 
remained so colourless in such a mixture as to render the P 
ence of amylum doubtful. It was therefore considered prefer: 
ey 
1) Bot, Zeitung 1885, p. 739. 
2) Nature, 1886, Dec. 16. 
3) The quickness with which iodine disappeared from the solution, made 
essary to close the tubes in which the leaves were coloured. 
4) Arbeiten Wiirzburg III p. 4. 
it nee 
