346 
Bottomley . — The Groivth of Lemna Plants in 
It was therefore decided to carry out a series of experiments with 
Knop’s nutrient solution, containing — 
Potassium nitrate, i grm. 
Potassium biphosphate, i grm. 
Magnesium sulphate, i grm. 
Calcium nitrate, 3 grm. 
Ferric chloride — a few drops. 
Distilled water, 6,000 c.c. 
The concentration of nutrient salts in this solution reaches about 1,000 
parts per million, as compared with 5,500 parts per million in Detmer’s 
solution. 
Fifteen dishes were arranged towards the end of September in three 
series of five dishes each : those of Series I, numbered from 1 to 5. each con- 
taining 150 c.c. of Detmer’s solution ; those of Series II, numbered from 6 
to 10, each containing 150 c.c. of Knop’s solution ; and those of Series III, 
numbered from 11 to 15, each containing 150 c.c. of Knop’s solution plus 
the water extract of J grm. of bacterized pea’t per i,coo c.c. of solution. A 
fourth series of five dishes, to which reference will be made later, was also 
inserted here, for the purpose of avoiding the duplication of the control 
series which would be necessary in a separate experiment. Twenty plants 
of Lemna minor were placed in each dish, and 300 similar plants counted 
out for an estimation of their dry weight, which was found to be 12*5 mg. 
for 100 plants. The same precautions for excluding light from bottom and 
sides of dishes, and for protecting them from dust, were observed as in the 
preceding experiments, and the liquids were renewed twice weekly, the 
greatest care being taken to prevent the growth of green Algae, which would 
supply organic matter to the solutions. Once a week the plants were 
counted, and they were halved at the weekly counting when necessary, one 
half being discarded. This did not happen, however, until the sixth week, 
for since the experiment did not end until about the middle of November, 
and was carried out in an unheated greenhouse, the rate of growth was 
extremely slow. The figures obtained for the eight weeks during which the 
experiment lasted are shown in the table below. 
Table I. 
Dish 
1 st 
2nd 
3 rd 
4 th 
5 th 
6 th 
7 th 
8 th 
Series. 
No. 
week. 
week. 
week. 
week. 
week. 
week. 
week. 
week. 
Detmer’s Solution 
1 
34 
64 
132 
200 
246 
304 
334 
420 
2 
40 
80 
164 
222 
273 
300 
348 
432 
3 
38 
76 
156 
202 
261 
324 
382 
434 
4 
39 
72 
160 
208 
244 
302 
366 
440 
5 
40 
82 
201 
2 39 
33 ° 
378 
456 
38.2 74.8 156.6 206.6 252-2 312.2 361.9 436.4 
Mean 
