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 ess in the leaves and roots of 
Drosera rotundifolia is probably trihyd thylnapthoquinon 
2. The rosette habit is conditioned by. enatenGba: 
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; 105-111; 129-154. 
Brissemoret, A., & Combes, R. (’07). Sur une réaction des oxyqui- 
nones. Jour. Pharm. et Chim. VI. 25: 53-58. 
Biisgen, M. (’83). Die Bedeutung des Insektenfanges fiir Drosera 
roleadatclia. 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. 
