WITH REFERENCE TO HORTICITLTURE. 



51 



and all the more vigorous-growing vegetables will grow in it most luxuriantly. 

 Hence, mixed with fine sand, leaf-mould is used as a substitute for heath- 

 soil, for growing many of the Cape and Australian shrubs; and alone, or mixed 

 with common garden soil, it is used for growing melons and pine-apples. 



181. Fresh and tender vegetables dug into the soil, produce an immediate 

 effect, from the facility with which they undergo fermentation, and thus 

 supply soluble matter for the spongioles. Sea-weed is still more readily 

 decomposed than recent land or garden plants, in consequence of the mineral 

 alkali which it contains ; and hence this manure is stimulating as well as 

 enriching. Malt-dust is valuable for the saccharine matter which it contains, 

 and rape-cake for its albumen and oil ; but these manures are oniy occa- 

 sionally to be met with. Straw, haulm, and in general all the stems and 

 leaves of herbaceous plants, and the shoots with their leaves on of trees and 

 shrubs, form valuable manure when decayed ; more especially, if from the 

 saccharine matter which they contain, or the addition of stable manure or 

 of animal matter, they can be made to heat and promote fermentation. 

 Nevertheless, without fermentation, they form useful garden manures ; or 

 moulds, which, like leaf-mould, may oft«n be substituted for heath-soil. 



182. The least valuable truly vegetable manure is spent tanner s bark, 

 which, consisting entirely of woody fibre impregnated with tannm, not only 

 contains no soluble matter, but the tannin, in as far as it can be taken up by 

 the spongioles, seems to prove injurious. Nevertheless, as every addition of 

 organic matter to a soil must ultimately increase its fertility, spent tanner's 

 bark may be used with a view to distant effects ; and in stiff soils its mecha- 

 nical action will be immediate, by rendering such soils for a time more open. 

 From the porosity and lightness of this material, it is an excellent non - 

 conductor of heat ; and hence, when laid on the surface of the ground as a 

 covering to the roots of tender plants, it protects tliem better from the frost 

 than a more compact covering, such as coarse sand, or than coverings vrhich 

 are great absorbents of moisture, such as leaves or half-rotten litter, or any 

 other covering of this kind which does not act as thatch. Rotten tan, how- 

 ever, being peculiarly favourable to the growth of fungi, should be used 

 with great caution when applied about young trees, and more especially 

 Conifer ai. 



183. Peat soil is of two kinds, that formed in peat bogs by the growth of 

 mosses, and that found in valleys, or other low tracts of country, which, being 

 formed of overthrown and buried forests, consists of decayed wood. The lat- 

 ter being the remains of a much higher class of plants than the former, must 

 contain a greater variety of the constituent elements of plants, and must conse- 

 quently be a better manure. Peat from bogs cannot be used till it has been 

 reduced, either by time or fermentation, to a fine mould or a saponaceous mass ; 

 the former result is obtained by exposure to the air, and repeated turnings 

 during several years, and the latter by fermentation with stable dung. A load 

 of this material, mixed with two loads of partially dried peat, will commence 

 the putrefactive process, in the same manner as yeast commences ferment- 

 ation in dough ; and, in the one case as in the other, additions may be made 

 by degrees of any quantity, so that two loads of stable-dung may be made to 

 produce twenty, a hundred, or in short an unlimited number of loads of fer- 

 mented peat. The peat of decayed wood is commonly reduced to mould by 

 exposure and turniag, and then applied to the soil, with or without lime. 

 Both kinds of peat are frequently burned for the sake of their ashes. 



