Mechanics of movement in Drosera rotundifolia* 
Henry D. Hooker, Jr. 
CONTENTS 
I. INFRODUC TION os <2) 4 ss jaran teea na eels ee ee tie a em eed meet eee 389 
ii BAPERIMEN TAL DATA sees iss Oe ee ee 3890 
1. OSMOTIC: CONCENTRATION Zhu oi fee a ea ape 380 
25 RARDONDS | 5 ox cece a ee fe See she a ee a ee ge, 393 
. AU NBENDING BY PLAGMOL YSIS aioe... oe cca tae cate eee PEE 304 
is & biactia nits ates Been ne Sas AMER Sa CN Coes ES DL VRE i oe 304 
INCREASED TURGIDITY AS THE MEANS OF MOVEMENT.............. 394 
(a) Osmotic concentration SC eae Mire en Seat com, ace eR EL Inee ari 395 
RGM EE Er CHUM 2 ok te Eg he ee, Se aot ak aehiaaeie Ree ae aa 307 
RG ASB WNE IASEICHV cs ssh e os oS ie oe ba a OS BS vA 307 
2. COMPARISON WITH GEOTROPIC MOVEMENTS..........0-.00.0000 eee 308 
B. ALTRRATION OF CELE<WALL BUASTICITY ¢ 2 6. SG Ss es 399 
4. AUTOTROPIC NATURE OF U PUES coe Bias wo ae Rt eatin re 400 
(a) Comparison of autotropic cai thie SHRUGS 52k Sass 400 
(b) Internal changes that follow bending..............0.000-0005 400 
Pere RR RTO Wor aks Gate rei E Cota ha trae RLte eG b Ee Wee SNe 402 
I. INTRODUCTION 
Plant growth is defined technically as any permanent change 
of shape or size produced by the activity of the plant (cf. Jost, ’13, 
Pp. 339; Pfeffer, 06, p. 1). The movements of Drosera tentacles, 
being reactions to stimuli, are determined by the activity of the 
Drosera plant. Moreover, bending is accompanied by a perma- 
nent elongation of the convex side of the tentacle and unbending 
by a corresponding increase in the length of the concave side 
(Hooker '16). These movements are therefore phenomena of 
growth. The term ‘‘growth’’ obviously includes a number of 
processes, which may be determined by changes in the amount of 
protoplasm, cell-wall material or osmotically active substances. 
II. EXPERIMENTAL DATA 
1. OSMOTIC CONCENTRATION 
In order to obtain a more detailed knowledge of the growth 
which brings about the movement of Drosera tentacles, the con- 
* Contribution from the Osborn Botanical Laboratory. 
