176 



GROWTH HORMONES IN PLANTS 



Fig. 52. — Course of geotropic curv^ature in coleoptiles of Hordeum placed 

 permanently in a horizontal position. The dotted line shows the growth of the 

 lower side; the dash line, the upper side. Note the increased growth of the 

 lower side. {After Weber, 1931.) 



Fig. 53. — Course of geotropic curvature in coleoptiles of Hordeum in the first 

 thirty minutes after placing them in a horizontal position. Dotted line shows 

 the growth of the lower side; dash line the growth of the upper side. Note the 

 alternation of the positive and negative growth responses. (After Weber, 1931.) 



