3 2o THE FOOD OF PLANTS 



Yucca filamentosa, but whether glucosides may appear as direct products of photo- 

 synthesis is doubtful '. Westermaier incorrectly supposed tannin to be an assimi- 

 latory product, and the pentoses do not appear to have any such direct origin a . 

 The same doubt applies to the imperfectly known paramylon found in Euglena and 

 other lower organisms, nor can anything be said as to the so-called cyanophycin 

 or the very problematic fucosan of Hansteen *. 



Oil. In higher plants oil has not as yet been proved to be a direct product of 

 carbon dioxide assimilation, for the oil-drops in the chloroplastids of Strelitzia 

 and other Monocotyledons do not disappear even during a prolonged sojourn in 

 darkness 4 . Similarly, it has still to be proved whether the oil, often present in 

 abundance in Vaucheria sessilis, &c., and in many Phaeophyceae and Florideae, is 

 a direct product of photosynthetic assimilation B . 



Chlorophyll. That chlorophyll is not a product of carbon dioxide assimilation, 

 as Gerland and Sachsse supposed, is shown by the fact that it remains present when 

 no assimilation is possible, and that etiolated plants turn green when exposed to 

 light in an atmosphere deprived of all carbon dioxide 6 . The same also applies 

 to chlorophyllan (hypochlorin), which Pringsheim erroneously supposed to be the 



1 Dextrose and laevulose : A. Meyer, I.e., pp. 467, 480, 487, &c. ; Schimper, I.e., p. 779. 

 Saccharose: Brown and Morris, Joum. of Chem. Soc., 1893, p. 660; Perrey, Compt. rend., 1882, 

 T. XCIV, p. 1124. Mannite : cf. A. Meyer, Hot. Zeitung, 1886, p. 145; 1885, p. 467 (sinistrin), 

 but according to Brown und Morris (1. c.,p. 660) inulin is formed in Yucca, and not sinistrin. Gluco- 

 sides : Brunner und Chuard, Ber. d. Chem. Ges., 1886, p. 609, but on insufficient grounds. 



2 Westermaier, Sitzungsb. d. Berl. Akad., 1885, p. 705. Cf. G. Kraus, Grundlinien z. Physiol. 

 d. Gerbstoffs, 1889, p. 46. Pentoses : Brown and Morris, 1. c., p. 162 ; de Chalmont, Ber. d. Chem. 

 Ges., 1894, p. 2722. 



3 Paramylon : Schimper, Jahrb. f. wiss. Hot, 1885, Bd.xvi, p. 199 ; Schmitz, ibid., 1884, Bd. xv, 

 p. in; Klebs, Unters. a. d. Bot. Inst. z. Tubingen, 1883, Bd. i,p. 272. Cyanophycin: Palla, Jahrb. 

 f. wiss. Bot., 1893, Bd. xxv, p. 554; Hansteen, ibid., 1892, Bd. xxiv, p. 346. [Crato (Ber. d. Bot. 

 Ges., 1893, p. 236) has shown that the supposed ' fucosan ' granules are really vacuoles ( = ' physodes ') 

 containing phloroglucin, and stain red with vanillin and HC1. Similar ' physodes ' are present in 

 abundance in the cells of many Phaeophyceae, sometimes giving the osmic acid, sometimes the 

 vanillin reaction, and occasionally both. The osmic acid reaction is not a conclusive test for the pre- 

 sence of fat or oil, while the phloroglucin may be an accidental by-product, and form but a portion 

 of the contents of the ' physodes.' Prolonged treatment with HC1 converts the readily disintegrating 

 vacnolar physodes of Ascophyllum into a fairly stable solid form (Church).] 



4 Holle, Flora, 1877, p. 133; Wakker, Jahrb. f. wiss. Bot., 1888, Bd. XIX, p. 474. Briosi's 

 conclusion (Bot. Zeitung, 1873, p. 529) that oil is the primary product of assimilation in Musa 

 cannot possibly be correct, and Ewart (Annals of Botany, Vol. XI, 1897, p. 446) has shown that in 

 Hoya fraterna oil-drops appear in the cells only when an abundance of starch has been formed, and 

 disappear before the starch does. It is evident that the utmost caution is necessary in drawing con- 

 clusions from data of this kind. 



* Vaucheria, &c. : Borodin, Bot. Zeitung, 1878, p. 498 ; Schmitz, Chromatophoren der Algen, 

 1882, p. 160; Schimper, Jahrb. f. wiss. Bot., 1885, Bd. xvi, p. 187; Wakker, ibid., 1888, Bd. xix, 

 p. 474. On starch in Vaucheria, see Walz, Jahrb. f. wiss. Bot., 1866-7, Bd. V, p. 129; on glucose, 

 Schimper, Bot. Zeitung, 1885, p. 779. Algae : Hansen, Mitth. a. d. Zool. Station zu Neapel, 1893, 

 Bd. xi, pp. 276, 283; Bruns, Flora, 1894, Erg.-bd., p. 159. On the occasional presence of 

 ' Floridaean starch,' see Hansen, I.e., p. 285; Golenkin, Algologische Notizen, 1894, p. 4; and 

 Bruns, 1. c., p. 177. 



' Gerland, Ann. d. Chemie u. Physik, 1871, Bd. CXLIU, p. 610, and 1873, Bd. CXLVin, p. 99; 

 Sachsse, Chemie u. Physiol. d. Farbstoffe, &c., 1877, p. 61 ; Phytochem. Unters., 1880, I, p. 3. 

 Similar suppositions are also quoted by Pringsheim, Chlorophyllfunction u. Lichtwirkung, 1882, p. 36. 



