Priestley and Ever shed. — Growth Studies. I. 229 
solutions were kept in large stock aspirator bottles, which were permanently 
connected to burettes with three-way taps. 
To each 600 c.c. bottle were added : 
10.8 c.c. KH 2 P 0 4 , M/ij 
3*0 c.c. Ca(N 0 3 ) 2 M/i l 
9-0 c.c. MgS 0 4 M/i J 
and the bottles were then filled up to the neck with tap-water. 
To each bottle were added seven drops of a fine suspension of ferric 
phosphate (0-2 grm. in 100 c.c. distilled water). The bottles in this experi- 
ment were placed in a specially constructed lead-lined wooden trough, in 
which they stood immersed in water above the shoulders ; the necks pro- 
truded through holes in black paper so that the roots developed in the dark. 
The water in the trough was kept continually flowing, and throughout the 
experiment the temperature remained very constant. The trough was 
placed on a laboratory table in a room with a glass roof, through which the 
cuttings obtained very satisfactory illumination. In warm weather the floor 
and table were sprayed several times daily to prevent the atmosphere from 
becoming too dry, and the plants throughout the experiment remained very 
healthy. 
1 12 bottles were accommodated in the trough, and the cuttings were 
started in them on July 13. They were as uniform as possible, and their 
weights varied between 3*5 and 4*5 grammes. 
The roots were collected and weighed separately, ten cuttings being 
taken on each date. 
The first roots were removed on July 22 and the last set were weighed 
on September 7. 
The culture solutions were renewed at intervals. The mean weights 
and probable errors are given in the following table, and the results are 
plotted in Fig. 2. 
Table II. Tradescctntia, Series //(see Fig. 2). 
Number of 
Mean weight of 
Mean weight of 
lays ’ growth . 
wet roots . 
dry roots . 
grm. 
grm. 
9 
0.08 + 0.01 
0-005+0.001 
11 
0-14 + 0.03 
0.008 + 0.001 
13 
o-i9±o-o5 
0.010 + 0.002 
14 
0.22+0.04 
0.012 +0-001 
1 5 
0.32 ±0.05 
0.017 + 0-001 
17 
0.31 +0-04 
0.016 + 0.002 
21 
0.43 ±0-04 
0-024 + 0-002 
24 
0-64 + 0.06 
0-034 + 0-003 
34 * 
0.75 ±0.09 
0-038 + 0-004 
45 
0.89 + 0.11 
0-043 + 0-006 
5 6 
0.84 + 0-13 
0.042 + 0-009 
In this series the secondary roots were first observed on July 26 and 
