145 
ness ; poppies are white before their development ; 
and carnations and roses do not acquire their rich 
hues but a short time before they are disclosed. 
Light, therefore, seems to act through the calyx of 
the flower in these instances ; but the greater num- 
ber of petals are green in the bud, before they are 
exposed to light. Others are white in the bud, and 
redden when they are disclosed *. 
40O. M. Becker made a great number of experi- 
ments on infusions of the flowers of different plants, 
by adding to them different acids, and various earthy^ 
metallic, and alkaline salts. In general, the acids 
produced in these infusions a red colour, and the al- 
kalis rendered them green, but sometimes yellow* 
In several instances, also, the nitric acid produced a 
yellow colour. All the acids reddened infusion of 
roses, but the alkalis and lime water rendered it yel- 
low, without passing through green. The expressed 
juices of various flowers were likewise changed, from 
blue or violet to red, by acids ; and brought back 
to their original colours by alkalis, which, if added 
in larger quantity, rendered them green or yellow. 
It results from these facts, that acids and alkalis ra- 
pidly change the colours of flowers ; that acids, ex- 
cept the nitric, render them red, (and it also reddens 
the infusion of roses), while a green colour is con- 
stantly produced by the alkalis. In the change from 
blue to red by acids, the colour passes through dif- 
ferent grades of purple ; and the green colour, pro- 
duced by the alkalis, passes ultimately to yellow. 
* Mem. Phyr. Chim. loir. :ii. 
K 
