132 PLANT PHYSIOLOGY 



regions, and they recommence longitudinal growth on application of external 



stimuli (Mc-EBius, 1899). 



1. 48, after BARANETSKY, 1901 read ; HARTIG, 1901 



1. 54, for grows at first in a straight line read straightens itself again ; 



436, 1. 8, for cell-walls, read cell-walls ; the convex side becomes more 

 extensible, and in unicellular organs the curvature must indeed depend on 

 an alteration in the extensibility of the cell-wall. 



437, 11. 20-1, for to obtain . . . phenomenon read from what has been said on 

 p. 422 about the amount of external work that can be done by turgid growing 

 organs. 



I. 23, for is about . . . purpose read requires about all the energy that is 

 actually available, 



1- 36, for latent read reaction 



II. 39-44, for As CZAPEK . . . klinostat read If after the end of this period 

 of stimulation the structures be placed in a vertical position, or, preferably, 

 rotated on a klinostat, geotropic curvature results later on. 



1. 48, for latent read presentation 



1. 49 P. 438, 1. 7, for It has in no case been found . . . twenty minutes. 

 read The presentation period in flower shoots of Capsella is about two minutes ; 

 in flower shoots of Sisymbrium and Plantago and in hypocotyls of Helianthus, 

 three minutes ; in other cases (plumules of Phaseolus, Vicia, Cucurbita, and 

 grasses) it may last from four to twelve minutes, and more rarely, e.g. hypocotyl 

 of Lupinus albus, it may amount to 20-25 minutes (BACH, 1907). As to the 

 time which elapses before the initiation of the reaction (latent period) it is 

 immaterial whether the organ be stimulated continuously or only until the 

 presentation period has been reached ; as soon as the geotropic stimulus has 

 operated for a period corresponding to the presentation period the minimum 

 latent period is obtained (BACH, 1907).] 



438, 1. 8, for latent read presentation 



1. ii P. 439, 1. 12, for If the root . . . klinostat. read Intermittent stimula- 

 tion may be brought about in a very simple manner by laying the object in 

 a horizontal position, then placing it upright and repeating the processes at 

 stated intervals. The klinostat may, however, be employed for this purpose. 

 First of all, DARWIN (1892), and later FITTING (1905), have used such inter- 

 mittent klinostats. FITTING'S apparatus permits of altering the period of 

 stimulation and the period of rest at will, and further enables one to place 

 the object not only alternately in the vertical and horizontal position, but to 

 combine any two selected orientations a point which will be found of interest 

 later on. Practically the same result may be attained, however, by means of 

 the ordinary klinostat, if the plant be placed so that its axis forms an angle 

 of 45 with that of the instrument, the latter itself forming an angle of 

 45 with the horizontal. When rotated the plant thus describes a cone in 

 space, and assumes alternately a horizontal and a vertical position. If the 

 klinostat be made to revolve as rapidly as possible without allowing disturb- 

 ances due to centrifugal force to take place, still geotropic curvature always 

 occurs. FITTING found that curvature took place even when the revolutions 

 were one per second, i.e. when the duration of the single gravitational stimulus 

 lasted only a fraction of a second. As yet it is uncertain whether it may, in 

 the long run, be possible to subject the plant to the action of gravity for so 

 short a period that no effect is produced, i.e. that no movement follows in con- 

 sequence of summation of individual stimuli. 



If summation of stimuli should finally lead to a curvature which the 

 solitary stimulus never induces, it may be interpreted only by assuming that 

 the solitary stimulus produces a certain change in the plant which persists for 



