under the Influence of Injuries. 5 1 1 
order to study the growth of the roots after the shoots were 
injured, the roots were marked with indian ink about 15 mm. 
from the tip (distance accurately measured) before the 
seedlings were placed in the glass boxes. They were then 
left for several hours in order to determine the normal rate 
of growth. The plumule or shoot was afterwards removed 
from the odd numbers, by means of a sharp knife or a pair 
of scissors, leaving the even numbers in a normal state for 
control-plants. In other experiments seedlings were pre- 
pared as above, but the shoots were split for several milli- 
meters instead of being removed. If it became necessary to 
remove one of the cotyledons in order to treat the plumule 
as desired, one cotyledon was also removed from each of 
the control-plants. 
In studying the growth of the shoot when the root was 
injured, the seedlings were prepared as before, and the shoot 
was marked near the base. In some cases only the root-tips 
were removed ; in other experiments nearly the whole root 
was cut away ; while in still other experiments the roots were 
split, either near the base or near the tip, for a distance of 
ten millimeters. Cultures in which the roots were grown in 
water or in damp chambers were especially convenient in all 
experiments in which the roots were to be treated, and in the 
study of the growth of secondary roots. 
To determine the effect upon the growth of the leaves 
when the tips of the leaves themselves were injured, seedlings 
of Arena, Hordeum , and Mats were grown in damp sawdust, 
and, after determining the rate of growth for a given number 
of hours, the tips of the leaves were cut off from two to 
fifteen millimeters. In like manner the effect was observed 
upon the growth of stems when an entire leaf was removed 
from the stems of Phaseolus , Vicia, and Cucurbita . 
A series of experiments were carried on to determine the 
effect of an atmosphere of ether upon growth. For this 
purpose Hordeum , Arena , and Secale were found convenient. 
The seedlings were grown in small pots of damp sawdust 
under large bell-jars. After the normal rate of growth had 
