446 The Botanical Gazette. [October, 
by a greater growth of xylem, and still in others by a com- 
bination of two or more of these methods. +1 
Corresponding results to those of Hegler if have recen : 
obtained in the roots of young plants of Helianthus cca 
and Cucurbita fepo, by attaching to the plants weights i 
pended over pulleys. In these experiments not only was ee 
tissue strengthened, but the roots grew with a larger diam 
ter than normally. a 
Thus far the attempt has been made to show that pier : 
unusually heavy stress has been laid upon the plant, the p rai 
responds by increasing the mechanical: tissue. But if 
plant be a self-re i 
Einfluss perim tiber 
— . these experiments as, R. Hegler’s Untersuchungen é 
89 von Zugkraft. Berd. k. sachs. Geselsch. d. Wissensch. December 
1891, 
