SUPPLEMENT 139 



457, 11. 39-42, for If it were . . . counteracted, read If, after a certain time, for 

 internal reasons, another surface should grow more vigorously, the apex of 

 the shoot must first of all be elevated, later on the side applied to the stick 

 would grow more rapidly, and hence the tension would be relaxed. 



458, 1. 18, for 1882 read Lectures 



I. 46, for AMBRONN, NOLL, and KOLKWITZ read AMBRONN (1884), NOLL 

 (1892, 1901), and KOLKWITZ (1895). 



459, 1. 2, after of them, read If, after decapitation, the apical end of a suitable 

 twiner be fixed, the free base performs twinings in a direction the reverse of 

 the original ; a left-handed twiner becomes a right-handed. This pheno- 

 menon is analogous with that discussed on p. 440. 



460, Lecture XXXVI is XXXV in 2nd German Edition. 



II. 26-39, f or From the analogies . . . with a window, read In order to 

 study heliotropism by itself it is necessary to exclude geotropism. This may 

 be done by allowing the plant to rotate in a vertical plane on a klinostat whose 

 axis lies horizontally, and at the same time arranging that light falls on it 

 on one side only, by placing the plane of rotation parallel to a window. 



462, 1. 15 P. 463, 1. 10, for Before considering . . . Fig. 146. read If we repre- 

 sent this conclusion in the form of a curve where light intensities are indicated on 

 the abscissa and heliotropic curvature (as measured by the angle of curvature) 

 on the ordinates we arrive at a diagram such as is represented at Fig. 146. 



463, 11. 21-4, for The problem . . . internal conditions, read The determina- 

 tion of the position of the other cardinal points of this curve has been only 

 partly settled. Thus FIGDOR (1893) has attempted to determine the lower 

 limits of light intensity which are still able to induce heliotropic curvature 

 when applied unilaterally. He found that in etiolated seedlings of Vicia Faba 

 this lower limit was about 0-002 normal candle-power. Still, other flowering 

 plants give other results ; Lepidium sativum still showed heliotropism when 

 the light was equivalent to 0-0003 candle-power, while 0-016 candle-power was 

 insufficient to induce curvatures in Raphanus sativus. 



Exhaustive research on other plants should be able to determine the 

 minimum light intensity impinging unilaterally, and, further, should allow 

 of the position of the other cardinal points being settled. So far, we know 

 that we have no constants to deal with ; on the contrary, the cardinal points 

 vary both according to external factors and internal processes. 



I. 36, for negative read a negative 



464, 1. 5, for unilateral read artificial unilateral 



II. 28-48, for It was already . . . relationship, read Over and above the 

 direction and intensity of light the wave length is of importance. It has long 

 been recognized that rays of different wave length do not act in the same way. 

 The more highly refrangible rays which are more especially concerned in the 

 formative activity of light (p. 310) have been found to be also those especially 

 concerned in heliotropism. WIESNER (1878) found that the rays at the limits 

 of the violet and ultra-violet regions were the most active, and that the activity 

 decreased from that point, so that, in yellow light, practically no heliotropic 

 curvature took place at all. The movements began again, however, in red 

 light and increased towards the ultra-red, although this was not true of every 

 plant examined. Negatively heliotropic organs, according to WIESNER, 

 behave like positively heliotropic ones. 



