HETEROMORPHOSIS 135 



the new stem from the upper portions. The new stems grew 

 upward, the roots downward. I have seen such new stems 

 arise, not only from the main stem and the main roots, but 

 also from the adventitious roots. Here also the new stems 

 always grew upward. Finally, I have seen new stems, which 

 also grew upward, arise from stems lying horizontally. 

 When, however, I cut off the tip from stems lying hori- 

 zontally, and regeneration occurred without heteromorphosis 

 or deformity of any kind, the new tip showed, so far as 

 my present experience goes, no tendency to bend upward. 



9. All newly formed stems arose from the upper surface of 

 the stem or root (see Fig. 19, s), it mattered not whether they 

 grew upon the main stem or upon the accessory roots. The 

 accessory roots sprang from the lower surface of the stems 

 when these lay horizontally. Whether all these phenomena 

 are determined solely by gravity I shall attempt to decide 

 by further experiment. 



10. That form of contact-irritability which I have called 

 stereotropism plays an important r6le in the growth of the 

 root of Aglaophenia. When the roots come in contact with 

 a solid body, they attach themselves to it (by means of a 

 secretion ?) and grow along its surface. This attachment is 

 a phenomenon of irritability which is called forth by contact 

 with the solid body itself; for when the root is brought in 

 contact with a solid body, it does not immediately stick to it, 

 but only after contact has lasted for some time (often as long 

 as twenty-four hours). Only the growing part (tip) of the 

 root is able to fasten itself to the surface of a slide. The 

 root adheres so firmly to the solid body that it is impossible 

 to separate the two by traction ; the root tears before it can 

 be pulled from the solid body. I have not as yet observed 

 the branches of Aglaophenia bend away from a solid body. 

 Yet I have proved with certainty that growing branches car- 

 rying polyps never attach themselves to a solid body with 



