230 
The Philippine Journal of Science 
1916 
greater in the light. But, as also previously suggested, I suspect 
that this was due to the atmospheric moisture. The average 
growth of reasonably active plants was usually greater in light 
than in darkness. Such an average is meaningless, unless the 
plants compared are at the same stage of the grand period of 
growth of the shoot being tested; but, if such averages are 
greater on the one side consistently, day after day, outside con- 
ditions may be regarded as responsible. However, there were 
constantly conspicuous exceptions to this rule, there being at all 
times from one-third to one-half of the varieties of which the 
most rapidly growing single plant was in the dark. 
Table II . — Growth of tubers of Dioscorea during one day, May 9 - 10 . 
Growth in millimeters. 
Col- 
lege 
No. 
Illumination. 
Without soil. 
Tuber No. — 
In soil. Tuber 
No.- 
1 
2 
S 
4 
5 
6 
7 
8 
9 
10 
I 
2 
3 
962 
6 
6 
19 
7 
4 
11 
1 
6 
2 
3 
1369 
12 
4 
2 
7 
6 
958 
14 
8 
6 
10 
1 
2 
960 
3 
6 
1 
3 
4 
7 
10 
40 
7 
16 
12 
33 
i 
5 
31 
9 
17 
4 
4 
62 
331 
1 Dark 
9 
16 
70 
26 
5 
4 
70 
157 
6 
135 
4 
4 
34 
951 
2 
5 
2 
2 
12 
6 
26 
1 
6 
3 
4 
88 
13 
3 
26 
10 
28 
25 
2 
2 
24 
39 
76 
116 
18 
4 
159 
97 
127 
26 
91 
6 
91 
121 
956 
2 
4 
2 
2 
4 
61 
4 
1 
1 
1101 
9 
11 
11 
2 
31 
41 
5 
14 
54 
71 
120 
3 
31 
3 
5 
5 
329 
7 
1 
2 
32 
7 
19 
5 
13 
5 
3 
18 
5 
6 
5 
16 
1094 
7 
7 
1 
2 
12 
2 
3 
938 
[Dark 
10 
7 
3 
1 
1 
