72S NOTES 



complex organic compounds of the transpiration stream; this accumulation is 

 sometimes so great that the walls become encrusted with solid matter." To the 

 author, Serin's arguments do not appear convincing. It would be a very peculiar 

 arrangement, if the chloroplasts had to obtain their supply of mineral salts from the 

 cell-walls ; what the importance of the " complex organic compounds " may be, 

 it is impossible to guess, as Senn gives no further information as to their chemical 

 nature. Even if we assume that the chloroplasts are attracted to the ventilated 

 regions of the wall in the manner suggested by Semi, we are not justified in concluding 

 that the physiological significance of this behaviour on their part has no connection 

 \i'h the intake of carbon dioxide. A carnivorous animal, though hunting by scent, 

 does not pursue its prey for the sake of the odoriferous substances, but in order 

 to obtain food- materials, which may themselves be quite odourless. As a matter 

 of fact, Senn has himself demonstrated that the chlorophyll corpuscles in the leaf 

 of Funaria display positive chemotaxis towards carbon dioxide (I.e. pp. 103-168). 



143. Knoll : Sitzb. Wien, 117, 1908. 



144. Pick : Beitr. z. Kenntn. d. assim. Gewebes armlaubiger Pflanzen, Bonn, 

 1881. 



145. Weber : Arb. Wurzb. 2, p. 343. 



146. Brogniart : Ann. Sci. Nat., ser. I., 21, 1830. G. Haberlandt : P.J. 13, 

 1881. Id. Ber. 4, 1886. Stahl : B.Z. 1880. Id. Jen. Zeitschr. 16, 1883 (sun- and 

 shade-leaves). Pick : Bot. Centr. 1882. Vesque : Ann. agron. 9 and 10, 1884. 

 Areschoug : Engler's Jahrb. 2, 1882. Heinricher : P.J. 15, 1884 (isobilateral 

 leaves). Kohl : Die Transpiration d. Pflanzen, etc., Braunschweig, 1886. Volkens : 

 Die Flora d. agyptisch-arabischen Wuste, Berlin, 1887. Nilson : Bot. Centr. 27, 

 1886 (photosynthetic tissue in stems). Eberdt : Ber. 6, 1888 (palisade-tissue). 

 Bonnier : Bull. Soc. Bot. France, 35, 1888, and C.R. 1890 (experiments on influence 

 of alpine climate on plants). Loebel : P.J. 20, 1889. Leist : Mitth. Naturf. Ges. 

 Bern, 1889, and Wagner : Sitzb. Wien, 101, 1892 (leaves of alpine plants). Rikli : 

 P.J. 27, 1895 (Cyperaceae). Montemartini : Atti. 1st. Bot. Pavia, 4, 1895. Jonsson : 

 Zur Kenntn. d. anat. Baues d. Blattes, Lund, 1896. Roedler : Zur vergl. Anat. 

 d. assim. Gewebesystems d. Pflanzen (Inaug.-Diss.), Berlin. Warming : Kgl. 

 Danske Vid. S., ser. VI., 8, 1897 (halophytes). Rywosch : Ber. 25, 1907. Rywosch 

 regards the tubular form of the typical palisade- cell as an adaptation to the prevailing 

 direction in which water flows through the mesophyll. As a matter of fact, no 

 appreciable flow of water takes place from the vascular bundles and spongy paren- 

 chyma towards the upper epidermis, for the simple reason that the latter is usually 

 devoid of stomata and in addition well protected against loss of water by cuticular 

 transpiration. Rywosch draws attention to the case of Asphodelus luteus, where the 

 uppermost layer of palisade-cells is richer in chlorophyll and shorter (in the radial 

 direction) than the more deeply seated layers ; he has failed to realise that the 

 more internal palisade-cells have to transmit the materials manufactured in the 

 overlying layers, besides disposing of their own synthetic products. Such differences 

 in the radial dimensions of different palisade -layers have no connection with trans- 

 mission of water. 



147. Noll : Arb. Wurzb. 3, 1888. 



148. Sachs : Arb. Wiirzb. 3, 1888. A. F. W. Schimper : B.Z. 1885. Brown 

 and Morris: J.C.S. 1893. A. Meyer: Uhters. iib. d. Starkekomer, Jena, 1895. 

 Rywosch : B.Z. 1908. 



[I48r(. This term is explained in the next paragraph. J 



