Aug. 15, 1921 
Effect of Ammonium Sulphate upon Plants 
705 
method, using the standard buffer mixtures and indicators recom¬ 
mended by Clark and hubs (/), and these concentrations were recorded 
in terms of P H values. 
The plants were grown in the culture solutions during a period of 
five weeks. At the end of the growth periods of the different experi¬ 
ments the dry weights of tops and roots of each culture were obtained 
separately by the usual method. 
I11 order to obtain information regarding the nonsolution environment 
of the plants daily records were kept, in so far as this was possible, of 
the measurements characterizing the aerial conditions. These data 
are briefly summarized in Table II, and in this form they provide some 
fragmentary evidence as to the sort of aerial conditions which prevailed 
in the greenhouse during the several experimental periods. 
Table II .—Maximum and minimum temperatures, average daily water loss by evapora¬ 
tion from standard white and black spherical atmomclers, and character of days for the 
different experiment periods 
Ex¬ 
peri¬ 
ment 
No. 
Experimental 
period. 
Air tem¬ 
perature. 
Average daily 
evaporation. 
Radio evapora¬ 
tion." 
Number of days. 
Beginning. 
Ending. 
1 
a 
i 
3 
Pi 
Maximum. 
Minimum. 
Average. 
Maximum. 
Minimum. 
i 
Average. 
I 
Clear. | 
Partly cloudy, j 
0 
0 
°c. 
°c. 
Cc. 
Cc. 
Cc. 
Cc. 
Cc. 
Cc. 
I. 
Jan. 19 
Feb. 28 
32.0 
6. 0 
23 - 7 
15-4 
17.8 
2.8 
2. 2 
2. 7 
14 
12 
15 
II.. .. 
Mar. 12 
Apr. 17 
35 - 5 
7. 0 
23 > 3 
12.4 
18. 9 
4.4 
1. 1 
2 ’ 5 
19 
7 
ri 
a The values given for radio evaporation represent the average daily excess of water loss from standard 
black spherical atmometer over that from the white. 
EXPERIMENTAL RESULTS 
For the sake of convenience in presenting the data, the two series 
of cultures here considered in connection with each experiment will 
be designated the Tottingham series (A) and the ammonium-sulphate 
series (B). It has already been stated that the two series as used in 
the different experiments are alike in every respect except that ammonium 
sulphate in equivalent osmotic concentrations was substituted in the 
solutions of the latter for the potassium nitrate in the former. 
In Table III are given the dry-weight yields of tops and of roots for 
the cultures of the two experiments considered. All yield values are 
expressed in terms of the value of the first culture (T1R1C1) in the respec¬ 
tive series considered as unity. The absolute yield value of this culture 
in grams is given just below the relative value 1.00 in each case. Since 
the high yields are always of greater interest than are the medium or low 
yields, the relative dry weights of tops and of roots from the six high- 
yielding cultures in each series are given in the table in bold-face type. 
