362 Bottomley.— The Effect of Organic Matter on the 
equally as possible. Each dish contained three plants with two leaves 
each, one with three leaves, and two with four leaves, a total of six plants, 
bearing between them seventeen leaves, in each dish. The solutions were 
renewed twice weekly, and a weekly record was made of the number of 
plants and leaves. During the fourth week of the experiment the dishes 
were found to be practically full, so the contents of each dish were halved 
as exactly as possible on October 16. The dry weight of one half of each 
was estimated, and a calculation made of the total weight in the dish. The 
other half of each set was retained and the experiment continued until 
Nov. 4, when growth was found to have practically ceased, for the experi- 
ment was carried out in an unheated greenhouse. The plants in each dish 
were counted, and the dry weight of the whole was determined. The 
results obtained are given below, and represent the figures corresponding to 
the complete sets at the respective dates. 
Table VII. 
Dish 
Sept. 22. 
Number of 
Oct. 16. 
Number of 
Weight 
Nov. 4. 
Number of 
' Weight 
Series. 
No. 
Plants. Leaves. 
Plants. 
Leaves. 
of set. 
Plants. 
Leaves. 
of set. 
L 
Detmer’s solution 
1 
6 
17 
40 
1 08 
gm. 
0*1612 
74 
184 
gm. 
0.3232 
2 
6 
17 
38 
IOO 
0*1496 
66 
192 
0*3172 
3 
6 
17 
36 
92 
0*1752 
68 
180 
0-3304 
4 
6 
17 
36 
100 
0-1728 
56 
174 
0*2968 
Mean 
« 
17 
37*5 
too 
0*1647 
66 
182.5 
0.3169 
II. 
Detmer’s solution 
5 . 
6 
7 
46 
no 
0*1896 
86 
248 
0.4840 
+ bacterized peat 
6 
6 
17 
48 
108 
0*1672 
76 
222 
0*4560 
7 
6 
17 
42 
102 
0*2092 
76 
202 
0.4388 
8 
6 
l 7 
44 
104 
0*1780 
78 
202 
o -4556 
Mean 
6 
17 
45 
1 06 
0* 1 860 
79 
218*5 
0.4586 
Thus on October 1 6, after three weeks’ growth, Series II, with organic 
matter, showed an increase of 12 per cent in the dry weight of the plants, 
and 6 per cent, in the number of leaves ; but on Nov. 4, after a further 
three weeks’ growth, the increase had amounted to 447 per cent, on 
the dry weight and 19 per cent, on the number of leaves. The plants in 
Series II appeared to be much more healthy than those in Series I, for the 
latter became very yellowish in appearance after the second week. The 
addition of the organic matter had a most marked effect on the health of 
the plants. 
Conclusion. 
The experiments recorded above demonstrate that the water plants 
employed all require a certain quantity of organic substance for their proper 
growth and development, and that they are unable to develop to their full 
extent in nutrient solutions containing minerals only. The maximum 
