ON ITS STATE OF CHEMICAL COMBINATION ? 95 



several substances in the plants in which they are found ? At 

 present we feed them all with the same kind of food in the same 

 form ought we to vary the form of combination with the 

 kind of plant, so as to arrive at the most certain ad most pro- 

 fitable result? Will less of the same substance produce an 

 equal effect in the case of each plant, according as we apply it 

 in this state of combination or in that ? 



Again, the necessity of nitrogen to the growth of all our plants 

 is now universally acknowledged, and it is believed that in many 

 instances ammonia is one of the forms in which it is most benefi- 

 cially and most profitably applied. But according to Persoz,* the 

 application of the smallest quantity of a solution of acetate, sul- 

 phate, or carbonate of ammonia, or of sal-ammoniac, destroys in 

 a short time the common pansy, (viola tricolor,} and a plant of 

 cobea scandens was in his experiments speedily killed by a solu- 

 tion of acetate of ammonia. 



Are we to conclude from these experiments that ammonia is 

 unsuited to these plants, and that their nitrogen must be ad- 

 ministered and taken in in another form ? or was it the state 

 of combination in which the ammonia was presented to the 

 plants that caused the injury ? In what state, in short, is nitro- 

 gen best adapted to each plant we grow ? and if ammonia be a 

 suitable form for all, in what state of combination, and how and 

 when should we add it to each ? 



We might put similar queries in regard to every substance, 

 organic or inorganic, which the perfect plant contains. But I 

 must not here dwell on these questions. The reader will not 

 fail to see, however, that the answer to them may introduce 

 very important modifications into the general rule (2) in 

 regard to the eifect of saline applications, which I ventured to 

 set down at the commencement of the present section. 



Fourth, The fourth cause of modification of our rule requires 

 no illustration. We have already seen that plants require eight 

 or ten mineral substances to build up their several parts. If 

 the soil be defective in a number of these, and the saline or 

 mineral application we make supplies only one of them, it is 



* Annalen der Chemie und Pharmacie, Ixv., p. 129. 



