350 Bottomley.— The Growth of Lemna Plants in 
the end of the eighth week. The figures obtained for the complete sets in 
Detmer's solution and in pond water each week are shown in the table 
below. 
Table IV. 
Dumber of 
Plants. 
16 
Series IV. Pond Water. 
Dish Number. 
1 7 18 19 20 Mean. 
Series /. Detmer's Solution. 
Dish Number. 
2 3 4 5 Mean. 
At beginning 
20 
20 
20 
20 
20 
20.0 
20 
20 
20 
20 
20 
20*0 
1st week 
30 
30 
31 
27 
32 
30-0 
34 
40 
38 
39 
40 
38*2 
2nd „ 
5 2 
55 
53 
49 
57 
53*2 
64 
80 
76 
72 
82 
74-8 
3 rd 
63 
72 
75 
69 
81 
72.0 
132 
164 
156 
160 
171 
156.6 
4 th „ 
92 
86 
89 
89 
9 1 
89.4 
200 
222 
202 
208 
201 
206-6 
5 th „ 
94 
no 
93 
109 
107 
102.6 
246 
273 
261 
244 
239 
252-2 . 
6th „ 
102 
1 1 6 
104 
114 
1 10 
109*2 
304 
. 300 
324 
302 
33 ° 
312.0 
7 th „ 
142 
122 
112 
1 26 
122 
124.8 
334 
348 
382 
366 
378 
361.9 
8th „ 
168 
156 
120 
160 
144 
149.6 
420 
432 
434 
440 
456 
436.4 
Weight of 
Plants in mg. 
6th week 
13-9 
15.8 
* 4*4 
T 5*4 
150 
14.9 
31-8 
31*9 
35-4 
30*6 
35-6 
V- 1 
33 -t 
8th „ 
2 2*4 
20-8 
18.4 
22-0 
19*2 
20*6 
32-0 
35*4 
37-3 
36-9 
38-3 
36*0 
A comparison of the mean weights and numbers of the plants in the 
two series for the sixth and eighth weeks gives the following figures : 
Table V. 
Series IV. Pond Water. Series I. Detmer's Solution. 
Average 
Average 
Calculated 
Average 
Average 
Calculated 
No. of 
weight 
weight of 
No. of 
weight 
weight of 
Plants. 
of Plants. 
100 Plants. 
Plants. 
of Plants . 
100 Plants. 
mg. 
mg. 
mg. 
mg. 
6th week 
109-2 
14*9 
13-6 
3 I2 *° 
33 * 1 
io-6 
8th „ 
1 49**6 
20-6 
13*7 
436*4 
36*0 
8-2 
The dry weight of ioo plants at the beginning of the experiment was 
12*5 mg., so that although the plants in pond water did not multiply so 
rapidly as did those in Detmer’s solution, they maintained and even 
increased upon their original size. They also retained their normal green 
colour throughout and were perfectly healthy at the end of the experiment, 
while those in Detmer’s solution diminished in size and became very 
unhealthy in appearance. 
It is thus evident that the pond water contained certain essentials for 
normal metabolism which were lacking in Detmer’s solution, though the 
rate of growth in the former medium appeared to be limited by the 
insufficient quantities of mineral nutrients, which were so abundant in the 
latter. 
An analysis of four samples of the water taken from the pond during 
four successive weeks showed an average content of 1,577 parts per million 
of total dissolved solids, of which 1,089 parts were inorganic and 488 parts 
consisted of organic matter. Further examination showed that the water 
