1900] GEOTROPISM OF STEMS Ig! 
In every instance the lower half grew more than the upper. 
July 14 the experiment was repeated with older plants. The 
average growth of nine plants in forty-eight hours was: in the 
upper half, 1.5™"; in the lower half, 2.2™™. In every instance 
except one the greater growth was made by the lower half. It 
occasionally chanced. that one half twisted into the other’s posi- 
tion, which caused the difference to be wanting or less marked. 
Later in the year in connection with work on other plants, I 
put five split plants into glass tubes too small to let them bend. 
The average growth of the lower halves in three days was 262": 
of the upper halves, 16™". At the same time I made a small 
attempt to see what is the rate of growth of a horizontal half 
stem in either position as compared to one in its natural erect 
position. Three plants were split throughout, and one half of 
each was put into an upright glass tube. In three days the 
average growth was 4.8™".. The other halves were put into 
horizontal tubes, with their split surfaces up, and grew in the 
same time on an average 14.3™". Of three other plants the 
average growth of the erect halves was 24™", and of the hori- 
zontal halves with split surface down, 244° 5 Oath two of these 
latter had twisted so that part of their growth was made with 
the cut surface up. The comparative growth of erect and hori- 
zontal halves was more fully experimented on with Lupinus. 
Phaseolus vulgaris. Three epicotyls, 4-5" in length, were 
split November 3, and the cotyledons were imbedded so that 
the split surfaces were horizontal. In three days the average 
growth of the upper halves was 3.2™™; of the lower, 5.7%". The 
curves necessary to bring the halves together were 95-145". 
November 20, six epicotyls were split, and the halves fastened 
in the same positions with glass needles. In two days the 
average growth of the upper halves was 25"; of the lower, 
27.2™, Small as the average difference is, the lower half was 
longer in every instance. 
Caladium sp. On large corms that had been brought into 
the greenhouse for the winter the stubs of the shoots were still 
Srowing slowly. These stubs were made up of some very young 
