THE SYNTHESIS OF STARCH. 159 



of Loew and Bokorny (Archiv f. ges. Physiologic, 1881, xxv, 150; xxvi, 50), Reiiike (Ber. 

 d. d. chem. Gesellsch., 1881, xiv, 2144), Mori (Nuovo. Gio. Bot. Ital., 1882, xiv, 147), 

 Pollacci (Atti d. instit. Bot. d. Univ. d. Pavia, 1900, vi, 45; Atti d. Real. Accad. d! 

 Lincei, 1902, xvi, 199), Grafe (Osterr. bot. Zeitschr., 190G, xlvi, I), Kimpelin (Conipt. 

 rend., 1907, cxliv, 148), Usher and Priestly (loc. ciL), Gibson and Titherly (Annals of 

 Botany, 1908, xxxii, 117), Bokorny (Archiv f. ges. Physiologic, 1908, cxxv, 467, and 1909, 

 cxxviii, 565), and Schryver (Proc. RoJ^ Soc., London, B., 1910, lxxxii, 226). Opposition 

 to the conclusions of some of the experiments has been offered by Loew and Bokorny 

 (loc. cit.), Plancher and Ravenna (Atti d. Real. Accad. d. Lincei, 149, xiii, 459), Czapeck 

 (Bot. Zeit., 1900, lviit, 153), Euler (Ber. d. d. chem. Gesellsch., 1905, xxxvii, 341), and 

 Bokorny {Joe. cit.). \Miile there may be reasonable doubt whether the presence of formal- 

 dehyde in plants in detectable quantities has been conclusively demonstrated, it seems 

 certain that it is formed, and that inasmuch as it is not in the nature of a storage substance 

 it is at once transformed into a saccharine body, and therefore that scarcely more than 

 traces could be expected to be found at any time. 



Another step in favor of formaldehyde constituting one of the primary metabolites 

 used by plants in the elaboration of saccharoses has been demonstrated in the power of a 

 plant to tlirive in a medium containing formaldehyde and in its power to assimilate it. 

 Work of this kind in showing one or the other or both of those phenomena has been carried 

 out by Bokorny (Ber. d. d. chem. Gesellsch., 1888, xxi, 119; Archiv f. ges. Physiologic, 

 1908, cxxv, 467, and 1909, cxxviii, 565), Bouillac and Giustiniana (Compt. rend., 1903, 

 cxxxvi, 1155), Treboux (Flora, 1903, lxxxxii, 49), Grafe and Vieser (Ber. d. d. bot. 

 Gesellsch., 1894, xxvii, 431), and Usher and Priestly {loc. cit.). While it has been clearly 

 shown that plants may thrive in a medium containing very small quantities of formalde- 

 hyde, and that some of the investigators also show that formaldehyde is absorbed, and 

 also that the plants may even thrive better in an atmosphere free from carbon dioxide if it 

 contain formaldehyde than when it does not, it has only been inferentially demonstrated 

 that formaldehyde is used in the plant in the synthesis of saccharoses. 



The several links of the chain constituting the synthesis of starch and glycogen may 

 be formulated hypothetically as follows: Carbon dioxide and water by deoxidation yield 

 formaldehyde, and perhaps other aldehydes; aldehyde by polymerization and atomic re- 

 arrangement yields sugars in the form of monosaccharoses ; monosaccharoses by dehydra- 

 tion yield disaccharoses; and these in turn by the same process yield polysaccharoses in 

 the form of achroodextrins ; achroodextrins by some form of intramolecular rearrangement 

 yield ery throdextrins ; cry throdextrins by some form of intramolecular rearrangment yield 

 starches or glycogens. Dextrins, glycogens, and starches are closely related polysaccha- 

 roses. Of the members of this chain the substances that are formed for storage purposes, 

 and therefore such as might be expected to be found in large quantities in plants, are 

 sugar, achroodextrin, erytlu-odcxtrin, glycogen, and starch. Of these, sugar and starch are 

 quantitatively preeminently important, but in certain plants they seem to be replaced 

 by glycogen or erythrodextrin. This scheme is, of course, modifiable in many ways, 

 inasmuch as the exact processes and primary substances in starch formation can not be 

 identical in all plants, or probably even at all times in the same plant. For instance, 

 when saccharose is utilizecl in this synthesis the process can not be identical with that 

 when maltose is used. The formation of saccharose must be on a somewhat different plan, 

 inasmuch as tliis sugar is of a distinctly different constitution, as is instanced in it not 

 giving many of the sugar tests, in its non-fermentability, and in its not reacting with 

 phenylhydrazine. 



There are various reasons for believing that in the synthesis of starch there are formed 

 thousands or even millions of stereoisomeric forms, each representing a homologue which 

 differs from the others. In the first place, the differences in the plastids of different species 



