1900 ] GEOTROPISM OF STEMS 193 
December 5. December 6, December 8— Growth from December 5 
Length in mm, Growth in mm, in mm, 
Lower half. Upper half. Former lower half. Former upper half, 
Ii 17 6 3 6 
2. 30 8 5 15 26 
=) 27 8 6 13 26 
4. 25 8 4 16 15 
Si 26 8.5 5 
6. 13 9 8 
7: 26 6 5 
8. 15 6 . 
9. 35 18 16 
The average growth of the under halves of the first four 
during the first day was 7.5™™: during the following two days, 
when they were the upper halves, their average was only 5.5™™. 
The average of the upper halves changed at the same time 
from 4.5™" to 13.75™". There is no possibility of error either 
from unequal splitting or individual variability in these results. 
Lupinus albus. The large, straight, solid hypocotyls of Lupi- 
nus are the finest subjects I have found for these experiments, 
and have been very freely used. November 15 four plants were 
split throughout, and imbedded at either end. After three 
days the average growth of the upper halves was 4.25"; of the 
lower halves, 10.5™™, The lower half was always the more 
curved, in spite of the tissue tensions which at first bent it 
downward. It was indifferent whether the cotyledons were 
split or separated. Of a number of plarits started November 17, 
and marked into 1™ zones, the following two were interesting in 
_ their behavior. Both twisted so that the halves changed posi- 
tions. After three days the growth of each half of one of them 
was 14™": at first the lower half gained (as was shown by ° 
Measuring the individual zones), and then after their positions 
Were reversed the other caught up. The upper and lower halves 
of the other plant grew respectively 15™™ and 13™™, but before 
they changed places the lower was 2™™ ahead. Of six plants 
split and put into glass tubes, November 28, so that they might 
Stow in length but could not curve, the average excess in length 
of the lower half after two days was 5™. Of seven plants 
