1905] MCCALLUM—REGENERATION IN PLANTS . 105 
days. Both stem and root elongated rapidly, at the expense of the 
food in the young plant to start with, so that part, probably most, of 
the food was used up, and the rest was distributed throughout the 
now much larger plant. Then the stem was cut off as close as possi- 
ble to the buds, and two of the plants were placed in the dark and two 
in the light. All four regenerated slowly. 
Experiment 7.—Twelve young plants were used as follows: a, 
two were cut off between the point of attachment of the cotyledons 
and the buds in their axils, so as to cut away the cotyledons and 
hypocotyl, leaving epicotyl with apex intact and primordia at the 
base, and set in a moist chamber; 6, from ten plants the cotyledons 
were removed and the stem cut off close above the primordia, then 
the hypocotyl was cut off immediately below the primordia, leaving a 
small piece of the stem (average 8™™ in length) with the primordia 
attached; five of these were set in darkness and five in light in a moist 
chamber, with the base of each piece resting on wet filter paper. In 
a there was no development of the buds; in 4, of the buds in the dark 
those on four plants grew to be 1-2°™ long and then died, presumably 
from starvation; while those in the light developed slowly at first 
and faster as they formed chlorophyll, finally forming shoots. 
These experiments show conclusively that when the young shoot 
is removed the removal also of the food supply does not hinder the 
development of the buds at the base, and that it occurs when there 
is not only no increase in the food, but when the primordia and the 
Surrounding parts are in a condition of starvation. Plants were 
grown in the most favorable conditions of rich soil, inorganic nutrient 
solutions, light, and moisture, so that vegetative growth was luxuriant, 
but only the removal of the apex had any influence in inciting the 
buds below to growth. The constant factor in every case is the removal 
of the apex, and neither an increase in food dependent on the removal 
of the growing shoot, nor any decrease that might occur in the nutri- 
tive relations constitute an essential part of the stimulus. 
In Bryophyllum Gorset (3, p. 420) says that the vegetative 
points serve as “centers of attraction for the constructive materials.” 
Those on the shoot, according to him, because of their more direct 
Connections with the conducting system act as stronger attractive 
centers than those on the leaves. Of the buds on the shoot the 
