192 
Walter Stiles and Ingvar Jorgensen. 
The differences in the rates of leaf development are thus about 
the same as in Series 1. After 50 days the increase is 44 per cent. 
The differences in dry weight after that time are similar. 
Aerated. 
Non-aerated. 
Shoot 
0-982 
0-623 
Root 
0-204 
0150 
Whole Plant 
1-186 4 0-083 
0-773 + 0 041 
— 
The increase in growth in the aerated cultures is thus 
53 per cent. 
Series 3. 
The solution used in this series was essentially that recom¬ 
mended by Pfeffer. It was constituted as follows: 
Calcium nitrate (cryst.) ... 
Magnesium sulphate (cryst.) 
Potassium nitrate 
Potassium chloride 
Potassium dihydrogen phosphate 
Ferric chloride 
Tap water 
1-00 gm. 
0-25 
0-25 
0-06 
0-25 
0-04 
... 100000 cc. 
Seeds sown in Sphagnum, June 20. 
Seedlings transferred to solution, June 26. 
Solutions changed, July 6, 14, 20, 25, 28, 31, August 3, 6. 
Cultures harvested, August 9. 
The leaf development was as follows: 
Days after sowing 
Number of Leaves 
Aerated 
Non-aerated 
10 
2 0 
2 0 
15 
3-0 
30 
19 
40 
4-0 
23 
5-8 
4-8. 
26 
70 
7-0 
30 
11-7 
9*9 
34 
15-4 
14-1 
43 
25-5 
21-2 
47 
29‘fi 
24-1 
The difference in the rate of leaf development in aerated and 
non-aerated cultures was thus considerably less than in the case of 
Series 1 and 2, the increase resulting from aeration being only 
23 per cent, after 47 days. Whether this is to be correlated with 
the differences in the culture solution or with unmeasured factors 
