GARDENING AS A SCIENCE. 
107 
good sand, rather than to apply an earth which, in too many instances, produces a 
sickly or uncertain vegetation. 
Having hinted at a probable cause of discoloration, to which we add that a 
plant can obtain little else than the soluble salts which exist in loam, — the earth 
itself being almost insoluble, — it may be inferred that the colour of foliage depends 
chiefly upon the vegetable matters which exist about the roots of plants ; and 
hence, that leaf-mould, properly reduced, is one of the best appliances that the 
gardener can resort to. 
This assertion is borne out in the instance of Lobelia ; for if in parterre-culture, 
one set of plants be " bedded out " in a loamy soil, and a second in one which 
consists almost entirely of two or three year-old leaves, the foliage of the latter will 
exhibit an intensity of verdure quite striking when compared with the yellowish, 
and therefore sickly hue of the former. 
In gardens where mushrooms are extensively cultivated, a great quantity of 
pure horse-droppings are employed : which, when the beds are exhausted, are 
found changed to a peculiar orange-coloured mass, approaching to mould. This 
substance is a modification of vegetable matter, and is extremely valuable in 
parterre gardening. We are certified of this by having closely observed the 
practice of a gardener, whose experience in floriculture extends to more than thirty 
years. He blends the old mushroom manure with a very good (proved) loam, 
digging out every small bed on the lawn, to the depth of 12 or 18 inches, and 
replenishing with this new compost. The effects produced are extraordinary : noble 
developments, dark verdant foliage, and most richly-tinted flowers, are the invariable 
results. Now it must be borne in mind that old horse-droppings are little more 
than vegetable remains, void of urinous or stimulating salts. Hence, they are 
speedily reduced in the soil, and, like leaf-mould, develop during their future decom- 
position the elements of water (oxygen and hydrogen), and also carbon, in a form 
wherein it can instantly combine, with hydrogen to form carburetted hydrogen, with 
oxygen to form carbonic acid, or with both, in varying, but appropriate quantities, 
exactly adapted to the habits of each individual plant. 
At this point we may appeal to chemical theory, and suggest that, as carbon, 
duly laborated, is certainly the cause of colour, the vital energy of a growing 
vegetable acts, first, (as a voltaic apparatus,) in decomposing the water or 
moisture of the earth in contact with the manure ; secondly^ that the stream of 
electricity, which invariably is produced whenever water is decomposed, dis- 
turbs and then decomposes the manure, developing its elements, and causing 
them to combine in definite proportions, precisely suitable to the constitution of 
each plant. 
This latter proposition is not fanciful ; for as it is certain that manures are 
more rapidly consumed during the growth of plants than when the ground is 
without crop, it follows that the disturbing forces must correspond with the 
peculiar energy exerted by each specific individual, and therefore that the new 
