356 Bottomley. — The Effect of Organic Matter on the 
green, and healthy in appearance. A comparison of the dry weights of the 
plants at this period gave the following figures : 
100 plants at the beginning in all series weighed 24*8 mg. 
100 plants after three weeks in Series I „ 20-4 „ 
» 5? >3 II » 44*8 „ 
3 ) 33 33 HI 33 47 *^ 33 
33 33 33 IV 33 4^*5 33 
These figures clearly indicate that Lenina major is not able to main- 
tain a good healthy growth in solutions containing only mineral nutrients, 
and that the addition of the various organic substances supplied corrected 
the deficiency and enabled the plants to grow more luxuriantly and preserve 
a thoroughly healthy appearance. The varying effect of the different 
substances added is chiefly shown in their influence on the rate of multipli- 
cation, for the weights of the plants in all the series containing organic 
matter were approximately equal, and all appeared equally healthy. 
It was pointed out that the plants used in these experiments were 
immature at the beginning, so a further trial was made in July, when a fresh 
supply of these plants came to hand, to determine whether fully-grown 
plants could remain healthy in inorganic nutrients only. 
Two series, each consisting of five dishes, were arranged, those of 
Series I, numbered from i to 5, each containing 200 c.c. of Detmer’s 
solution, and those of Series II, numbered from 6 to 10, containing 
a similar quantity of the same solution, which also contained the water 
extract of 1 grm. of bacterized peat in every 500 c.c. Ten full-grown plants 
of Lemna major were placed in each dish, and three hundred similar plants 
used for an estimation . of their dry weight. The dishes were treated 
precisely as before, for four weeks, and the following figures were obtained : 
Table II. 
Series. 
Dish A r o. 
1st week. 
2nd week. 
3rd week. 
4th week. 
I. Detmer’s solution 
1 
16 
20 
21 
30 
2 
13 
18 
20 
29 
3 
13 
17 
20 
26 
4 
12 
16 
19 
25 
5 
18 
21 
28 
Mean 
13.8 
17*8 
20-2 
27-6 
II. Detmer’s solution + 
6 
24 
4 8 
99 
166 
bacterized peat 
7 
28 
53 
113 
1 97 
8 
26 
50 
104 
173 
9 
25 
49 
9 2 
168 
10 
24 
5 i 
1 03 
192 
Mean 
2 5'4 
50.2 
102-2 
177.2 
The plants in dishes 2, 5, 6, and 8, which were nearest to the mean, 
were pressed and mounted as a permanent record, and photographs of these 
