VALUE OF AMMONIA AND NITRIC ACID. 303 
by Kuhn, that so soon as ammonia was taken up by the 
plant, the acid with which it was combined, becoming free, 
acted as a poison. 
In 1866, Hampe (Vs. S¢., IX., 165), using phosphate 
of ammonia as the single source of nitrogen, and taking 
care to keep the solution but faintly acid, obtained a 
maize-plant which had a dry weight of 18 grams, includ- 
ing 36 perfect seeds; no nitrates were formed in the 
solution. 
The same summer Kihn (Vs. Sé., [X., 167) produced 
two small maize-plants, one with phosphate, the other 
with sulphate of ammonia as the source of nitrogen, but 
his experiments were interrupted by excessive heat in the 
glass-house. 
In 1866, Beyer ( Vs. St., [X., 480) also made trials on 
the growth of the oat-plant in a solution containing bi- 
carbonate of ammonia, The plants vegetated, though 
poorly, and several blossomed and even produced a few 
Seeds. Quite at the close of the experiments the plants 
suddenly began to grow, with formation of new shoots. 
Examination of the liquid showed that the ammonia had 
been almost completely converted into nitric acid, and the 
increased growth was obviously connected with this nitrifi- 
cation. 
In 1867, Hampe ( Vs. St., X., 176) made new experi- 
ments with ammonia-salts, and obtained one maize-plant 
2’|, ft. high, bearing 40 handsome seeds, and weighing, 
dry, 25'|, grams. In these trials the seedlings, at the 
time of unfolding the sixth or seventh leaf, after consum- 
ing the nutriment of the seeds, manifested remarkable 
symptoms of disturbed nutrition, growth being sup- 
pressed, and the foliage becoming yellow. After a week 
or two the plants recovered their green color, began to 
grow again, and preserved a healthy appearance until 
mature. Experiment demonstrated that this diseased 
state was not affected by the concentration of the nour- 
