26 Hooker: Physiological observations 



small. The bending region is confined to a very short basal 

 portion of the pedicel. 



Transitions from exterior to central tentacles occur, which 

 exhibit intermediate conditions not only in their structure but 

 also in their behavior. It is probable that some of these tentacles 

 are both nastic and tropic. 



8. Summary 



1. The red pigment which is found in the leaves and roots of 

 Drosera roiundifolia is probably trihydroxymethylnapthoquinone. 



2. The rosette habit is conditioned by transpiration. 



3. The inflexion of Drosera tentacles is produced by an accelera- 

 tion of the rate of growth on the convex side and in the median 

 section. The unbending is caused by an increase in the rate of 

 growth on the concave side and in the median section, accom- 

 panied by compression of the convex side. 



4. In both cases the acceleration commences near the base and 

 extends toward the gland. The amount of growth is greatest 

 near the base and decreases apically. 



5. A tentacle is capable of reacting three times. During each 

 reaction an apical portion of the bending region becomes fully 

 grown. Drosera tentacles have intercalary, basipetal growth. 



6. The bending of the exterior tentacles is nastic; of the central 



tentacles, tropic. The unbending is in all cases owing to auto- 



tropism. 



Sheffield Scientific School, 

 Yale University 



Literature cited 

 Batalin, A. ('77). Mechanik der Bewegungen der insektenfressenden 



Pflanzen. Flora 60: 33-39: 54-58; 65-73; 105-II1; 129-154- 

 Brissemoret, A., & Combes, R. ('07). Sur une reaction des oxyqui- 



nones. Jour. Pharm. et Chim. VI. 25: 53-58. 

 Biisgen, M. ('83). Die Bedeutung des Insektenfanges fiir Drosera 



rotundifolia. Bot. Zeit. 41 : 569-577; 585-594. 

 Darwin, C. ('08). Insectivorous plants. Revised by F. Darwin. 



London. 

 Darwin, F. ('08). Experiments on the nutrition of Drosera rotundifolia. 



Jour. Linn. Soc. Bot. 17: 17-32. 



