dioxide by roots is another evidence that in many eases 

 at least, roots actually do respire much as do the aerial 

 portions of plants." This does not mean, however, that 

 11 roots respire in the normal manner or that respira- 

 tion "by means of free oxygen is the only kind of repjiira- 



1. Knop,- Ann. Ghem. Pliarm. 129 ; 287 (1864); 

 Gorenwinder,- Ann. sci. nat. (5) _9: 63 (1868); Deherain 

 and Vesque,- G. R. 84: 959 (1877); Czapek,- Jarhb. wiss. 

 Bot. 2y : 321 (1896); Hall,- ocience Prog, 1: 51-57 

 (1906); otohlasa and Ernest,- Gentbl. Bakt., Abt# 2, 



14: 723-736 (1905), Zeits, Zuckerind. Bohmen 31: 291- 

 307 (1907), Jahrb. wiss. Bot. 46: 55-102 (1908); P.eed,- 

 Pop. 3ci. L r on._73: 257-266 (1908). quantitative experi- 

 ments on the amount of COg excreted by roots have been 

 made by Kossowitsch but apply to' water-cultures only. 

 Zhur. Opyt. Agron. 5_: 482-493 (1904), 7: 251 (1906). 



2, 2he supposed aerotropism of roots reported 

 by Ilolisch lias been questioned by Bennett and dammet and 

 is probably hydrotropism: Ilolisch,- Situngsber. Akad. 

 ,/iss., .;ien, Abt. I, 90: 194 (1884), 102: 423 (1893); 

 Bennett,- Bot. Gas. 37: 241 (1904); dammet,- Jahrb. wiss, 

 Bot. 41: 611 (1905). Upward curvature of roots in water- 

 logged joils has been observed by several authors; dee 

 Jost,- Bot. Ztg. 45_: 169 (1887); Goebel,- Bot. Ztg. 45: 

 717 (1887); Schenk,- Jahrb. wiss. Bot. . 0: 534,564, 569 

 (1889); .,'ieler,- Jahrb. wiss. Bot. 52: 503 (1898). It 

 is possible, however, that this may be due to negative 



