On the Cultivation of Orchards. 
381 
Devon, can form but a faint conception of the effect of the heaven- 
showered orchards, blended as it is with all else that excites our ad- 
miration of the prodigal bounty and beauty of nature. Witness the 
valley of the Dart, with very many others. The general prevalence 
of orchards in these districts, and their greater productiveness than 
in others, sufficiently indicate that the apple-tree requires a soil 
more or less calcareous ; and from the best fruit being produced by 
orchards situated upon the red marls of Hereford and the other 
counties, we may likewise infer that a considerable portion of clay 
is necessary to the perfection of its produce. Great light has been 
lately thrown upon the adaptation of soils to particular plants ; 
and it is now easy to account for the predilection, so to speak, of 
the apple-tree for soils that abound in clays and marls. All de- 
ciduous trees require a considerable portion of potash for the 
elaboration of their juices in the leaves, and are prosperous or 
otherwise in proportion to the plentiful or scanty supply of that 
substance in the soil. Liebig has shown that the acids gene- 
rated in plants are always in union with alkaline or earthy bases, 
and cannot be produced without their presence.* The most 
striking exemplification of this necessity is the vine, the leaves, 
tendrils, and unripe fruit of which are remarkable for their 
acidity. It has been proved that vineyards supplied with manure 
of a very forcing kind, but which contains no potash (horn- 
shavings, for instance), soon cease to be productive. Now the 
apple-tree, during its development, produces a great quantity of 
acid ; and therefore, in a corresponding degree, requires alkaline, 
and probably earthy bases also, as an indispensable condition to 
the existence of the fruit. Without such substances therefore in 
the soil, in adequate abundance, orchards cannot prosper ; and it 
is morally certain that more accurate inquiry and observation will 
establish the fact, that, all other things being equal, they are pro- 
ductive or otherwise in proportion to the quantity, up to a certain 
limit, of these substances in the soil. It is known that all clays 
contain potash, and that marls consist of clay and carbonate of 
lime, and also contain potash, besides sulphate and phosphate of 
lime. The presence of alkaline and earthy bases, particularly 
potash and lime, affords a satisfactory solution of the adaptation 
of marly soils to the production of apples, even without taking 
into account the part which phosphate and sulphate of lime play 
in their formation. These considerations are very interesting, as 
they are calculated to throw a valuable light upon an important 
branch of horticulture and rural economy, by pointing out the 
means of exercising an effectual influence upon soils in the pro- 
duction of apples which are not naturally adapted to that pur- 
* Chemistry of Agriculture and Physiology, p. 92. 
