Hooker: Movement in Drosera rotundifolia 391 



tacle by way of the gland at the apex and the broken end at the 

 base where the tentacle was formerly attached to the leaf blade. 

 In many cases it was found necessary to puncture the cuticle in 

 several places with a needle, or else to cut the pedicel into segments 

 with a razor, in order to give the solutions access to all the cells of 

 the tentacles. 



1. Straight tentacles. — Examination of over thirty normal 

 marginal tentacles with potassium nitrate and of twenty with 

 glucose solutions showed the cells of the apical half of the pedicel 

 to have a higher osmotic concentration than the cells of the basal 

 half. The latter ranged from eight to nine atmospheres; the 

 former from nine to eleven. In a few instances the cells on the 

 dorsal and ventral surfaces of the basal portion of the pedicel 

 had a higher osmotic concentration than the cells on the flanks. 

 De Vries ('86, pp. 4, 5) found that the cells of Drosera tentacles 

 were plasmolyzed by a three percent, solution of potassium nitrate, 

 but not by a two per cent, solution. This is seen to hold for all 

 the stalk cells excepting those at the apical end just below the 

 gland. 



2. Bending tentacles. — The glands of numerous tentacles were 

 stimulated by rubbing with a fine brush and after fifteen to twenty 

 minutes, when the tentacles had bent through an angle of 90° to 

 120°, the><l were removed and placed in a two percent, potassium 

 nitrate solution. This treatment did not cause the tentacles to 

 unbend. They were then mounted in some of the same solution 

 and covered with a supported cover-glass. Since the tentacles 

 were curved, the different effect of the solution on the convex and 

 concave sides of the tentacle could be observed. In nearly all 

 cases where the movement was rapid, the two per cent, potassium 

 nitrate solution had plasmolyzed the cells in the bent region on the 

 convex or abaxial side, while the cells on the concave or adaxial 

 side showed no effect. Similar results were obtained by using a 

 5.4 per cent, glucose solution. Examination of fifty tentacles with 

 potassium nitrate and of thirty-five with glucose showed the osmotic 

 concentration in the abaxial cells to be from six to eight atmos- 

 pheres, in the adaxial cells from eight to nine atmospheres. The 

 osmotic concentration of the cells on the convex side had therefore 

 diminished during bending; that of the cells on the concave side 



