NOTES 740 



323. Gaulhofer : Ber. 26^, L908. 



324. Gaulhofer : Sitzb. Wien, 117, 1<)08. 



325. G. Haberlandt : Die Lichtsinnesorgane d. Laubbliitter, Leipzig, 1905, pp. 

 86 sqq. Id. Ber. 1906. Id. Biol. Centr. 27, 1907. Id. P.. I. 46, 1909. Kniep : Biol. 

 Centr. 27, 1907. Nordhausen : Ber. 1907. Gius : Sitzb. Wieri, 116 (1907). Albrecht : 

 Ber. 1908. Id. Ub. d. Perception d. Lichtrichtung i. d. Laubblattern (Inaug.-Diss.), 

 Berlin, 1908. 



326. Mention should be made of a curious experiment carried out by Kniep 

 (I.e. [325]). The upper surface of leaves of Tropaeolum minus, Begonia discolor 

 and B. heracleifolia were wetted with paraffin oil, with a refractive index of 1 -476. 

 The resulting distribution of light on the inner epidermal walls was the converse 

 of the normal arrangement, there being now a dark central area and a bright marginal 

 zone ; the dark spot was, of course central in vertical illumination, but excentrically 

 situated in oblique light. The illumination of the inner epidermal wall was therefore 

 still differential, and, as a matter of fact, Kniep's leaves adjusted themselves more or 

 less accurately to the prevailing light, even after being wetted with paraffin. Kniep's 

 results by no means conflict with the author's theory of light-perception ; they 

 merely show that the central portions of the ectoplast on the inner epidermal wall 

 are not necessarily " attuned " to intense light, nor the marginal area to feeble light. 

 Evidently, the power of perception depends not upon adaptation of the ectoplast 

 to bright or dull light, but upon its power of distinguishing between symmetrical 

 and asymmetrical illumination ; this power naturally presupposes a general capacity 

 for recognising differences of light-intensity. 



327. Eye-spots. Zimmermann : Beih. Bot. Centr. 1894, pp. 161 sqq. (Sammel- 

 referat). Engelmann : Pfliiger's Archiv, 29, 1882. Strasburger : tlber Reduktions- 

 teilung, etc., Jena, 1900, p. 193. Wager : Journ. Linn. Soo. (Zool.) 27, 1900. 

 France : Zeitschr. f. d. Ausbau d. Entwickelungslehre, 1908. 



328. The extensive literature dealing with the transmission of stimuli has been 

 carefully compiled, and critically discussed by Fitting : Ergebn. d. Phys. 4 and 5 

 (also published as a separate work under the title : Die Reizleitungsvorgange b. d. 

 Pflanzen, Wiesbaden, 1907). 



329. Rothert : Conn's Beitr. 7, 1896. p. 137. Czapek : P.J. 32, 1898, pp. 217 



sqq. 



330. Kretzschmar : P.J. 39, 1903. 



331. Fitting : P.J. 39, 1903. 



332. Pfeffer : Physiology, 2, 1901, pp. 90 sqq. and 199 sqq. 



333. Tangl : P.J. 12, 1879-81. Id. Sitzb. Wien, 92. Russow : Sitzb. Dorpat, 

 6. Gardiner : Arb. Wiirzb. 3. Kienitz-Gerloff : B.Z. 1891. Arthur Meyer : B.Z. 

 1896. Id. Ber. 1897. Kuhla : B.Z. 1900. A. W. Hill : Proc. Roy. Sue. 67 B, 

 1901. Kohl: Ber. 1900. Strasburger: P.J. 36, 1901. 



334. Pfeffer : I.e. [282], p. 524. 



335. G. Haberlandt : I.e. [274], p. 30. 



336. G. Haberlandt : I.e. [274], p. 106. 



337. A. W. Hill : Phil. Trans. 149 B, 1901, p. 10:5. 



