44 BRECK’S NEW BOOK OF FLOWERS. 
principally upon the degree of oxygenation. In leaves 
fully developed the chromule is green; it gainsa tendency 
to yellow or red when it is more oxidized, as one per- 
ceives by the changes of the color of leaves in autumn, by 
the effect of acids; and it appears to verge to blue when 
it is less oxidized. We know that the flower of the Hy- 
drangea becomes blue in a soil sufficiently impregnated 
with iron.” 
“The nature of this work does not admit of a very ex- 
tensive discussion of this subject in its pages, but it may 
be well to show that plants do contain metallic oxides.” 
“Dr. Sprengel, in a German publication called Der Land 
und Hauswirth, or the Agricultural and Domestic Econo- 
mist, states that in almost all plants analysis discovers more 
or less iron, and as the atmosphere does not contain any 
sensible quantity, it must. be admitted that it is derived 
from the soil.” 
“In Sir Humphrey Davy’s Agricultural Chemistry, it is 
stated that the only metallic oxides found in plants are 
those of iron and manganese, but there is little doubt that 
copper exists in the Rose, as may be verified by leaving a _ 
clean linen rag in rose water or in the water in which 
rose leaves have been steeped; after some days it will 
turn green, and copper may be detected, even when the 
rose water has been distilled in glass or new tin vessels. 
I remember to have seen a scientific account in some 
French publication, of gold being extracted from the sage 
plant, although in very small quantities. Iron and manga- 
nese would however be sufficient to produce almost every 
variety of color known.” 
“Immediately after the flower withers, a change in the 
juices of most plants takes place, by which change the 
fruit or seed is matured; this is very perceptible in the 
eatable fruits, and proceeds until acidity becomes obvious 
to the taste; after this saccharine juice is formed—now if 
