Mineral Solutions and in their Natural Medium . 347 
Dish 
1st 
2nd 
3 rd 
4 th 
5 th 
6 th 
7 th 
8 th 
Series. No. 
week. 
week . 
week. 
week. 
week . 
week. 
week. 
week. 
II. Knop’s Solution 6 
28 
60 
93 
*59 
202 
256 
268 
286 
7 
33 
62 
102 
161 
200 
2 44 
282 
316 
8 
27 
62 
90 
158 
201 
256 
264 
308 
9 
32 
61 
93 
152 
209 
240 
302 
354 
10 
32 
66 
101 
166 
230 
278 
328 
372 
Mean 
30*4 
62*2 
95.8 
159.2 
208*4 
254.8 
288.8 
327.3 
III. Knop’s Solution + 11 
36 
60 
1x8 
207 
286 
42 2 
562 
740 
Bacterized Peat 1 2 
35 
73 
1 37 
247 
354 
456 
590 
754 
13 
33 
69 
127 
220 
322 
408 
570 
73 ° 
14 
38 
74 
125 
237 
310 
470 
684 
848 
15 
34 
68 
123 
225 
3T0 
428 
604 
804 
Mean 
35*2 
68-8 
126-0 
227.2 
316.4 
436.8. 
602-0 
775*2 
The dry weights of the half-sets which were discarded in the sixth 
week were estimated, and a similar determination was made at the conclusion 
of the experiment, the following comparison for the three series being 
obtained : 
6 th week. 
Table II. 
8 th week. 
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. 
Series I. 
312 
33 *i 
10.6 
436 
36.0 
8.2 
Series II. 
255 
27.4 
10.7 
3 2 7 
29.2 
8*9 
Series III. 
437 
75 *2 
17.2 
775 
124*0 
i ;*3 
Owing to the advanced season of the year, the rate of growth in all the 
series was extremely slow as compared with that obtained in other experi- 
ments, recorded in the previous work, 1 which were carried out during the 
growing season under conditions of fairly high temperature and continuous 
sunlight during the greater part of the day. However, the experiment 
demonstrates quite clearly that Knop’s solution is no more able than is 
Detmer’s to supply the plants with all that they require to maintain their 
normal health. In the former solution the weight of 100 plants depreciated 
from 12*5 mg. at the beginning to 8-9 mg. at the end, while in the series 
supplied with organic substance the plants showed not only a more rapid 
rate of multiplication, but also an increase in individual size, the weight of 
100 plants at the end of the experiment reaching in this series 17*3 mg. 
Experiment with Lemna major . 
A similar experiment had also been arranged and carried out with 
Lemna major a little earlier in the season, being started at the end of 
August. A set of twenty dishes was divided into four series of five dishes 
each. Those of Series I, numbered from 1 to 5, each contained 150 c.c. of 
1 Bottomley, W. B. : Proc. Roy. Soc., B, vol. Ixxxix, 1917, pp. 481-507. 
