PROOFS OF ACID SOILS. 71 



eacli plant is greatly retarded ; but if the whole growth of an acre 

 were estimated, it would probably exceed in quantity the different 

 growth of the richest soils, of the same age and on an equal space. 

 Every cultivator of corn on poor light soil knows how rapidly 

 sorrel* will cover his otherwise naked field, unless kept in check by 

 continual tillage and that to root it out, so as to prevent the like 

 future labour, cannot be effected by any mode of cultivation what- 

 ever. This weed too is considered far more hurtful to growing 

 crops, than any other of equal size. Yet neither of these acid 

 plants can thrive on the best lands. Sorrel cannot even' live on a 

 calcareous soil ; and if a pine is sometimes found there, it has 

 nothing of its usual .elegant form, but seems as stunted and ill- 

 shaped as if it had always suffered for want of nourishment. In- 

 numerable facts, of which these are examples, prove that these acid 

 plants must derive from their favourite soil some kind of food pe- 

 culiarly suited to their growth, and quite useless, if not hurtful, to 

 cultivated crops. 



2d. Dead acid plants are the most effectual in promoting the 

 growth of living ones. When pine leaves are applied to a soil, 

 whatever acid they contain is of course given to that soil, for such 

 time as circumstances permit it to retain its form, or peculiar pro- 

 perties. Such an application is often made on a'large scale, by 

 cutting down the second growth of pines, on land once under till- 

 age, and suffering them to lie a year before clearing and cultivating 

 the land. The invariable consequence of this course is a growth 

 of sorrel, for one or two years, so abundant and so injurious to the 

 crops, as to more than balance any benefit derived by the soil from 

 the vegetable matter having been allowed to rot. From the gene- 

 ral experience of this effect, most persons put pine land under 

 tillage as soon as cut down, after carefully burning (to destroy) the 

 whole of the heavy cover of leaves, both green and dry. Until 

 within a few years, it was generally supposed that the leaves of 

 pine were worthless, if not hurtful, in all applications to cultivated 

 lajid which opinion doubtless was founded on such facts as have 

 been just stated. But if they are used as litter for cattle, and 

 heaped to ferment, the injurious quality of pine leaves is destroyed, 

 and they become a valuable manure. This practice is but of recent 

 origin but is highly approved, and rapidly extending. [Still 

 later it has been found that when these leaves are applied unrotted, 

 as raked up in woodland, to calcareous land, they produce only and 



* Sheep sorrel, or Rumex acetocella. The wood sorrel (Oxalis acetocelld) 

 is of a very different character. The latter prefers rich and even calcareous 

 soils, and I have seen it growing well on spots calcareous to excess. It 

 would seem, therefore, that wood sorrel forms its acid from the atmosphere, 

 and does not draw it from the soil, as I suppose to be the case with common 

 sorrel. [The wood sorrel is a trefoil, and pod-bearing or leguminous 

 plant.] 



