392 Hooker: Movement in Drosera rotundifolia 



had remained practically unchanged. The greatest diminution 

 in the osmotic concentration of the cells on the convex side was 

 observed in those tentacles that reacted most rapidly. In a few 

 cases of exceptionally slow movement no diminution was observed, 

 the osmotic concentration being either eight or nine atmospheres. 

 The osmotic concentration of the cells in the upper half of the stalk 

 was found to be the same as in the unbent tentacle. 



3. Bent tentacles. — Tentacles were stimulated by placing small 

 flies on their glands, and after bending had proceeded as far as 

 possible the tentacles were removed and examined. In twenty- 

 five tentacles treated with potassium nitrate solutions and fifteen 

 tentacles treated with glucose solutions, the cells at the base of 

 the pedicel and in the bent region had an osmotic concentration 

 of nine to eleven atmospheres, there being no difference between 

 the two sides of the tentacle. The cells of the apical portion of 

 the pedicel were found to have an osmotic concentration of ten 

 to thirteen atmospheres. In a few exceptional cases the cells in 

 the latter region appeared to have a higher osmotic concentration, 

 but the detection of plasmolysis was particularly difiticult because 

 these cells were smaller than the basal cells and their contents 

 were strongly aggregated. 



4. Unbending tentacles. — Twenty tentacles in process of un- 

 bending were examined with potassium nitrate solutions and the 

 results were checked by the examination of twelve more with 

 glucose solutions. The osmotic concentration of the cells in the . 

 basal half of the pedicel was from eight to ten atmospheres; in the 

 apical half from nine to eleven. No difference was observed in 

 the osmotic concentrations of the cells on the concave and convex 

 sides. 



5. Unbent tentacles. — Eighteen tentacles which had become 

 straight after completing a reaction were examined and found to 

 be similar in osmotic concentration to the normal tentacles before 

 reaction. 



The experimental data given above are summarized in the 



following table: 



Three significant facts should be noted, namely: 



I. The osmotic concentration of the pedicel cells increases 



from the base to the apex. 



