138 STuDIES IN GENERAL PHYSIOLOGY 
pluma; the new apex, however, was not so regularly formed. 
Occasionally a lateral branch was missing upon the side of 
the main stem. In the majority of the experiments, how- 
ever, such figures as are shown in Figs. 20a and 206 were 
formed. A new piece be at first grew vertically upward 
from the main stem ab until the new stem ce was formed, 
which usually grew vertically upward; the polyps of this new 
stem ce were all located upon the upper surfaces of the lateral 
branches, so that the new stem ce was oriented symmetri- 
cally to the old stem ab with respect to a horizontal axis. 
After this the main stem began to grow horizontally and 
finally downward. 
2. The newly formed parts be arising from the prolonga- 
tion of the main stem, and,growing at first horizontally and 
then downward, all possessed the contact-irritability of 
roots, namely, positive stereotropism. When brought in 
contact with solid bodies, they attached themselves to 
their surfaces and behaved like the roots of Aglaophenia 
pluma. Only the growing parts of the roots were able to 
attach themselves in this way. Here also the influence of 
contact stimuli in determining the point of origin of 
branches again showed itself. While the branches arose, 
almost without exception, from the upper surface of the root, 
when it was surrounded by water, they were formed upon the 
side opposite the solid substratum upon which the roots grew, 
in roots which were attached to the surface of a solid body. 
The experiments were made in an aquarium which was 
far removed from a window, and into which only very weak 
light fell almost horizontally. In spite of this, the branches 
grew vertically. This seems to indicate that light has no 
influence in this case in determining the place where new 
organs are formed. 
The protoplasm retracted from that portion of the branch 
which was buried in the sand. 
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