1896.] Anatomical and Physiological Researches. 299 
perature stimuli are doubtless due to their direct influence on 
the osmotic action of the cells.” ? 
Correns finds that the most various kinds of solutions, so 
dilute as to cause no injury, call forth in tendrils a typical re- 
action. Since the cuticle is with difficulty penetrated, rather 
strong solutions are sometimes necessary to cause the reac- 
tion, e. g., iodine solution, 0.00192 %. Even stronger 
concentrations of other substances cause no injury and call 
forth the reaction, e. g., acetic acid, 2-6 %; arsenic, I %; 
chloroform, 10 %. Ammonia vapors also cause a plain reac- 
tion, 
MacDougal found that when tendrils were submersed in 
Solutions of the ordinary metallic salts (no concentrations 
given), “the induced osmotic action quickly caused curves.” 
Unless penetrated and killed immediately, the tendrils were 
thrown into coils. ® 
In the case of the chemical stimulus Correns finds that 
accommodation takes place when the concentration of the 
solution is gradually increased. : 
A few experiments with induction currents renders it prob- 
able that they too are able to produce reactions similar to 
those described. é 
Correns studied the tendrils of Cucurbitacee and Passi- 
floras mainly, but other tendril-bearing forms were not neg- 
lected.—Ropney H. TRUE. 
The physiology of Drosera rotundifolia. 
In his work on Drosera rotundifolia, Darwin* arrived at the 
“onclusion that the speed with which the tentacles show cur- 
Vature reactions varies according to the temperature, from 
488°C. to 51.6°C. being especially favorable. 
t. Carl Correns® regards this conclusion, that a ber aa 
vation releases irritation movements, to be worthy 0 
* Bor. G 
- Gaz, 18: 
Da a 18: 12 
3 Bor. Gaz. 17: 207. 1892. 
sc j 
: 1893. I 
ter Insectivorous Plants 66. 1875. [Ed. I. 
Correns, Bot. Zeit. 54: 21-26. 1896. 
