177 
GARDENING AS A SCIENCE. 
No. VIII. 
We made allusion in our late article, No. 6, to the utility of leaves for almost 
all the purposes to which manure is applied, inasmuch as they contain the elements 
of vegetable organization. And a few general remarks were then offered on a plan 
adopted at one establishment for the alternate production of strawberries and melons 
in a bed of earth consisting chiefly of decayed leaves. 
For a work devoted to Floriculture, it is not strictly in keeping to enlarge upon 
the operations of the kitchen-garden ; the few more particular remarks which the 
subject calls for, must therefore be restricted to the agency of vegetable matter 
upon ornamental plants exclusively. 
It would be most fortunate could we correctly ascertain, and demonstrate, the 
effects which certain modifications of decaying organized substances produce upon 
certain plants : take as an example the Hydrangea hortm&is. Occasionally a 
specimen with blueish flowers is met with : blue they are not, the hue they assume 
being that of a French gray, or fading lilac ; but as a variety, numbers of inquiries 
have been made, and pretended answers given, not one of which appears to be 
relevant to the subject. 
We are assured by a nurseryman, whose word is veracious, that there is a 
species of heath-mould miscalled peat, which, beyond a doubt, has converted the 
pink tint of an Hydrangea into blue. The fact may be so, or it may not ; but we 
have an example now of a plant in bloom, which proves beyond question, that a 
very fine, strong Hydrangea, transferred to pure Bagshot heath soil, will prosper 
therein exceedingly. This plant has upon it two large heads of pink flowers, not 
in the least altered by the change of its soil. But if the bloom be the same, the 
foliage is astonishingly improved : each leaf is very large, firm in texture, and of 
an intense, full green, totally different from the yellow hue which results from the 
use of loam. 
This luxuriance and verdure evince that to the black vegetable matter of heath 
soils, though it amount to little more than one-tenth of their substance by weight, 
we must ascribe their nutritive power. Our repeated analyses, more than once 
referred to, have also proved that the remaining nine-tenths of the earth consisted 
almost entirely of white, or silver sand. We know also that the verdure of 
Camellia Japonica is exalted by the use of black bog earth (heath soil), and 
therefore we consider one principal point in the science of Floriculture to be 
unquestionably established. 
The exposure of erroneous inferences is, or ought to be, a primary object in all 
physiological investigations : and thus, in discovering the efficacy of vegetable 
earths, we have detected the fallacy of the theory which had ascribed the change 
of tint in Hydrangea to the presence of iron in the soil. 
VOL. X. NO. CXVI. A A 
