322 BOTANICAL GAZETTE * [APRIL 
a result of decapitation and amputation, together with a consideration of the 
physiology of stimulus transmission in tendrils and in Mimosa. 
When tendrils of Passifora sp. are severed at the base, a strong apical 
curvature appears in one or two minutes. This curvature is limited to the 
haptrotropically sensitive zone and becomes corrected if the tendril has its 
cut surface in water. Both curvature and recurvature are true growth phe- 
nomena, being dependent upon an accelerated growth of the middle zone. 
Similar responses may be obtained with tendrils belonging to widely differ- 
ent families, although minor modifications appear. In some tendrils a fluid 
drop exudes from the exposed surface, and in others no such drop appears. 
The incision must enter the central cylinder in order to produce a curve. 
Piercing with a fine needle is a stimulus if the central cylinder is penetrated. 
The impulse travels from the locus of amputation toward the motor zone very 
rapidly, even as fast as 20™™ per second, and the actual rate is probably 
greater because the larger portion of time elapsing between stimulation and 
response is to be considered asa latent period. 
From old and new experiments it is evident that the process of transmit- 
ting a wound stimulus in Mimosa coincides in all essential particulars with 
such a process in tendrils. All indications are that in Mimosa transmission 
occurs in the living cells. Since in some cases an impulse is carried beyond 
a deadened zone it seems improbable that the plasma actively participates in 
the transmission. Haberlandt’s theory of a diminution of hydrostatic pres- 
sure in the conductive tissue as an explanation of the transmission process 1S 
inadequate because it occurs in plants which are without Schlauchzellen.— 
RAYMOND H. Ponp. 
