No. 4.] (COMMERCIAL FERTILIZERS. 135 



Dr. VooiiiiKKS. Yoii can i)ut on a wliolc lot of phosphoric 

 acid, and leave ont the other elements, and the plant will 

 api)ear to ripen qnieker. 



]\Ir. Crafts. I am a tobacco grower, and that, in this 

 valley, is one of the important indnstries. In growing a 

 cro}) of tobacco we want (pialitv, bnt it is desirable to have 

 the tobacco ripen in reasonable time ; we mnst get it ripened 

 and ready to harvest before frost, and early enough so it 

 will mature j)ro])erly. It was a question in my mind whether 

 a sui'plus of j)hosi)lioric acid which we derive from bone and 

 other sources would tend to keep that plant growing vigor- 

 ously until too late in the season. 



Dr. VooRiiEES. I don't think so. I can see very easily 

 liow we might change the character of the growth by adding 

 an excess of one, or displacing one, when we wanted to get 

 an abnormal growth. But I do not think you would get it by 

 tliat means. It would make it ripen quicker because of the 

 lack of the other food. When it ripens too soon it is because 

 the conditions are not favorable for it to obtain all the food. 

 !N^ow, phosphoric acid in excess does encourage that, but it 

 won't do so unless it hasn't enough of the other materials 

 present. I know very little about tobacco growing from the 

 practical side. But it does not seem to me it would do it in 

 that way. But you might get an abnormal growth there, 

 which might be of more value to you than a normal growth. 

 In onr market-garden crops we don't get normal growths. 

 That is, the natural tendency is to grow to maturity; but we 

 don't want maturity. We apply an abundance of nitrogen, an 

 excess of nitrogen, and we get an abnormal growth. 



Question. You think an excess of- nitrogen would cause 

 longer gTowth, more luxuriant growth, than the phosphoric 

 acid? 



Dr. VooRiTEEs. Certainly. 



QuESTiox. And you don't think phosphoric acid would 

 contribute to that ? 



Dr. VooRHEEs. Xo, not in the same way. 



Mr. W. H. BowKER (of Boston). Dr. Voorhees, have you 

 read the last " Science Monthly," in which Dr. Hall speaks of 

 soluble phosphoric acid as hastening maturity ? Do not 



