
No. 458] | GEOTROPIC RESPONSE IN STEMS. 83 
Table T.— Continued. 



Time |Nocur- Curvature at Deviation of 
No. Material. Temp. | Hrs. Min. | vature. degrees 135 degrees 
291| Raphanus sativus | 222 C | 4— o 8 18 3 apparently 
221 n B 21°C | 6— 30 7 14 I 
311| Brassica alba 229C| 4— o 3 28 o 
25% " " 21°C} 6—30| ıı 14 o 
211| Helianthus annuus | 219 C | 6 — 30 7 13 I 
395 53 133! it 







Number showing curvature, 342 
Percent of these showing curvature for deviation of 90 degrees, 96.8. 
[73 [14 & [14 “ « “ & [23 135 « 32. 
AFTER-EFFECT METHOD. 
By this method, orthotropic plant members are exposed to the 
one-sided action of gravitation by being placed out of their 
normal position; but before a geotropic curve has time to 
appear, the plant is put upon the klinostat and so revolved that 
the further curving effect of gravitation is neutralized during the 
revolution, Thus any geotropic influence induced in the plant 
before the plant was placed on the klinostat has opportunity to 
manifest itself. If, now, the gravitation effect on plants differs 
according to the deviation of the plant from its normal position, 
we may expect the size of the after-effect angle attained on the 
klinostat to be greatest when the previous exposure of the plant 
» was made at the angle of optimum stimulation. In other words, 
this method may possibly be used to aid in the discovery of the 
angle of optimum stimulation. 
It was believed that results obtained by exposing stems for 
the short period to the gravity-stimulus would be more reliable 
than those of Czapek who forcibly prevented all curvature of 
the roots and hypocotyls used while exposing them for hours to 
the action of gravity in each of the two positions, and thus, it 
would seem, making it possible for the long continuance of a 
weak stimulus to equal the effect of a stimulus in reality 
Stronger. 
! Results quoted from Professor Newcombe by permission. 
