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. 



