dO 



Jesenko 1 reports an effect of carton dioxide in shorten- 

 ing the rest period of trees. According to Gorrens 2 

 excess of carbon dioxide lowers the irritability of 

 Mimosa and Darwin 3 reports that it causes the closing of 

 stomata. Molish^ and Rothert^ have observed a supposed 

 negative tropism of roots to carbon dioxide and Engelmann^ 

 obtained a shock response of Bacterium photometricum to 

 sudden changes in the concentration of carbon dioxide 

 although no similar response occurred on mere replace- 

 ment of the air by hydrogen. Protoplasmic streaming 



1. Ber. deut. bot. Ges. 30: 81-95 (1912). 



2. Flora 75: 109 T 121, 130 (1892). 



3. Darwin,- Proc. Roy. Soc. 63: 413-417 (1898). 



4. Sitzungsber. Akad. V/iss., '.Vien, 90: 172, 

 194 (1884), but see the contrary observations of Bennett 

 and Sammett noted on page » , note • 



5. Plora,- Ergzbd. : 216 (1894). 



6. Pflug. Arch. 30: 112 (1882); Bot. Ztg. 



: 689 (1888). On chemotaxis of Pararnaecium toward 



carbon dioxide see Jennings,- Jour. Physiol. 51 : 318 

 (1897). 



