CONDITIONS OF PLANT-GROWTH. 19 



dance of phosphoric acid, for instance, in the soil, yet the 

 plant might starve for want of phosphoric acid, because it 

 -•vas utterly unavailable. And thus for forty years have 

 scientific men been moving backward and forward in relation 

 to the principles of plant-nutrition, — experimenting, investi- 

 gating, discovering gradually fact after fact, — until to-day it 

 can probably be said with truth that there is almost universal 

 harmony and unanimity of opinion among scientists in rela- 

 tion to the subject of plant-nutrition, and that that opinion 

 has been sustained and upheld by the natural fact and law of 

 the case. 



It may not, therefore, be out of place if I speak for a mo- 

 ment of this belief of scientists in relation to plant-nutrition. 

 In the first place, it is agreed, — and, gentlemen, I wish you 

 would mark the language I use, — it is agreed among scientists 

 that, so far as the plant is concerned, there is no difference in 

 the importance and value of either of the two great classes 

 of matter, — organic and inorganic. No plant can grow and 

 make a perfect growth unless it has a supply, in such propor- 

 tions as it needs, of both elements of matter, — organic and 

 inorganic. That is, if the plant has access to all the mineral 

 elements of nutrition it needs, those mineral elements of 

 nutrition are utterly valueless in the production of the plant 

 unless in some way the plant can obtain at the same time all 

 it requires of the inorganic elements of nutrition. Again, 

 that so far as the organic elements themselves are con- 

 cerned, neither one of these elements, so far as the plant 

 is concerned, is of more importance than any other. For 

 instance : carbon is just as important to the plant as nitro- 

 gen ; nitrogen is just as important to the plant as carbon. 

 Nitrogen, however abundant in form calculated to give the 

 plant nourishment, is worthless to the plant unless the plant 

 can in some manner obtain the needed carbon. And so with 

 the other two elements of organic nutrition. So, too, with 

 the mineral elements of plant-food. Lime being abundant 

 in the soil, is of no account to the plant unless at the same 

 time it can get its required quantity of soda, of iron, of pot- 

 ash, or any other of the inorganic elements of nutrition. 

 All, so far as the plant is concerned, are of equal importance. 

 Another belief is, that the maximum quantity of crop to be 



