1905] MCCALLUM—REGENERATION IN. PLANTS 115 
system had been removed, roots promptly came at these watered 
areas. 
These experiments show that contact with or the free absorption 
of water by the stem, or the complete saturation of the stem and 
whole plant, will not induce root development on the stems when the 
roots below are intact. 
On the other hand, the roots may develop when the 
< [> parts from which they arise not only do not absorb any 
Ble water, but are actually wilting. From a considerable 
7F $<| number only four experiments will be mentioned. 
CSS 
Experiment 26.—Plants were cut off near the base and 
the whole plants placed in damp air, the lower free end of 
the stem being suspended in the air and not in contact 
with water. A slow transpiration necessarily occurred and 
the plants gradually wilted. The lower end of the stem 
became quite dry, yet from it roots arose. 
e538 Experiment 27.—Three pieces of 
internodes were placed in damp. air. 
They wilted until there was a conspicuous shrink- 
age, and yet at the basal end. of each roots de- 
veloped. The weight of the pieces at the begin- 
ning of the experiment was 8.7%", and eight days 
later, when roots had just appeared, 7.9%. 
Experiment 28.—Stems were cut off near the 
base, and a portion of the upper part of the inter- 
node was surrounded by water, as shown in jig. 8. 
The lower part projected downward through a 
hole in a glass plate and was in the rather dry 
air of the laboratory; while over all the rest of 
the plant was placed a bell jar to keep the air / 
moist so that the plant would not wilt. Roots 
soon came out from the part of the stem sur- 
rounded by water. The basal end projecting 
down into the air became somewhat wilted, especially toward the base 
Where the end for about 1°™ was completely dried up. In spite of 
this, roots formed just above this dried portion, and broke through 
the epidermis but could not continue in the dry air. 
