No. 129.J 419 



ly follow one another is a fact now universally admitted. Dc- 

 candolle, Macaire and others supported a theory that the exuda- 

 tion from one class of plants, while poisonous to themselves 

 afforded food and nourishment to those of a difierent genus. 

 The researches and discoveries of more modern chemists have, 

 however, given us a clearer and better perception of the wonder- 

 ful workings and agencies of nature as regards the matters re- 

 quired in the raising and building up of crops. Thus, for in- 

 stance, they have ascertained that wheat requires more silica 

 than beans, and that beans require more potash than w^heat. 

 Hence the advantage of one crop of these following the other. 

 Professor "V^ay states that the potash of clay soil exists in them 

 as silicate of potash derived from the felspar, &c., of the disinte- 

 grated rocks to which the clay owes its origin. The silicate of 

 potash in felspar is composed of silica and potash in tolerably 

 equal quantities ; but a crop of wheat takes off 83 parts of sili- 

 ca for every 14 parts of potash, so that to obtain all the silica it 

 requires, it liberates more potash than it has any need of I A crop 

 of beans just reverses this process : it removes from the soil 70 

 parts of alkali for every 5 parts of silica. It is then almost in- 

 different which of the plants come first. The one which follows 

 in rotation finds potash (if beans) or silicia (if wheat) ready 

 prepared for it. The same sort of rule holds with regard to the 

 elements and mode of assimilation of plants of other crops." . 

 Extracts by H. Meigs. 



[From the RcYue Horticole, Paris, June, 1861.] 



Moss on Fruit Trees. — The destruction of this is requisite for their 

 health. These Cryptogames must be removed, for the health of 

 trees is as important as that of animal?. The poets pretend that 

 the mosses planted on trees preserve a humidity which is necessa- 

 ry to their vegetation, and that they in turn give the tree a poetical 

 aspect, and that they preserve the tree from rigorous cold; and 

 that by a wise foresight of nature they are justly placed on the 

 north side of a tree on which they appear numerous and tufted 

 This reasoning, judicious as it appears at first sight, does not suit 

 many cultivators, for they prefer beautiful and vigorous trees to 

 mossy ones, and we partake of that opinion ourselves. 



