PEAE BLIGHT. 



on the subject, would have us to understand that there is a strong analogy in the life 

 principle of plants and animals. It is, therefore, fairly inferable that, as animals of 

 the same species do not wholly depend on one class of food for life and health, but 

 that, to a certain extent, choice is left to select from, producing the same results, that 

 this is equally applicable to plants. When we, therefore, have the analysis of Prof. 

 Emmons before us, showing that the ash of the sap-wood of the Pear tree contains 

 more than twenty-seven per cent, of phosphate of lime, twenty-two of potash, and a 

 number of other inorganic elements, though perfectly correct, are we sure that a 

 tree grown in a diflferent soil will not produce different results ? I shall show that this 

 is the case in other species of trees, and therefore infer it is so with the Pear. It is 

 very certain that the color of fruits is affected by substances in the soil and taken up 

 by the roots, not essential or detrimental to the health of the tree. 



LiEBiG, in speaking of the inorganic constituents of plants, says : " Many of the 

 inorganic constituents vary according to the soil in which the plant grows," <fec. 

 Again: "Most plants, perhaps all of them, contain organic acids of very different com- 

 position and properties, all of which are in combination with bases, such as potash, 

 soda, lime, or magnesia," &c. ; and after proceeding to show that certain acids are 

 always, of necessity, present in plants, he proceeds : " It is equally certain that some 

 alkaline base is also indispensable in order to enter into combination with the acids." 

 And, while he seems to make it clear that the life and health of the plant depends 

 invariably on certain acids, he says : " It will be necessary to bear in mind that any 

 one of the alkaline bases may be substituted for another, the action of all being the 

 same." His object is, if I understand him, to prove that certain acids are in the first 

 place essential to the existence of the plant, and that this always attracts a given quan- 

 tity of alkaline ; that these alkalines are not necessarily the same, but similar in action ; 

 that the plant will take them up as they are found in the soil. To prove this, he says : 

 " It has been distinctly shown, by the analysis of D'Saussure and Berthier, that the 

 nature of a soil exercises a decided influence on the quantity of the different metallic 

 oxyds contained in the plants which grew on it; that magnesia, for example, was con- 

 tained in the ash of a Pine tree grown at Mont Brever, while it was absent from the 

 ash of a tree of the same species from Mont La Salle ; and that the proportions of 

 lime and potash were also very different." Again he adds : " Let us now compare 

 Bertiiikr's analysis of the ash of two Fir trees, one of which grew in Norway, and 

 the other in Allerard, (departemens de I'lsere.) One contained fifty, the other twenty- 

 five per cent, of soluble salts. A greater difference in the proportion of the alkaline 

 bases could scarcely exist between two totally different plants." 



Though it seems in all cases the oxygen was found nearly in the same quantities in 

 each species, proving conclusively that while certain properties, such as some of the 

 acids and oxygen, are always present in nearly uniform proportions, that it is not so 

 with other substances ; that they not only vary largely in quantity, but in some 

 instances are altogether absent ; that a tree, like an animal, has some latitude of choice 

 food ; and that the elements of the air are essential to the existence of both, 

 is perfectly in harmony with every day's experience of the different and diverse 



