THE CONVERSION OF THE PRODUCTS OF ASSIMILATION. II 157 



Bibliography to Lecture XII. 



Beijerinck. 1895. Centrbl. Bakt., Abt. II, I, 221. 



BoKORNY. 1 90 1. Bot. Centrbl. 85, 293. 



Bredig. 1 90 1. Anorganische Fermente. Leipzig, 



Bredig. 1902. Ergebnisse der Physiologie (Spiro-Ascher), i. 



Brown and Morris. 1890. Jour. Chem. Soc. Trans. 57, 458. 



CzAPEK. 1903. Ber. d. bot. Gesell. 21, 229. 



DucLAUX. 1899. Traite de Microbiologie, II. Diastases. Paris. 



Emmerling. 1 90 1. Ber. d. chem. Gesell. 34, 600 and 380. 



GoDLEWSKi. 1879. Bot. Ztg. 37, 97. 



Green, J. R. 1901. Die Enzyme (German edition by Windisch). Berlin. 



Gruss. 1897. Jahrb. f. wiss. Bot. 30, 645. 



Hanriot. 1901. Compt. rend. Paris, 132, 146. 



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Hill. 1898. Journ. Chem. Soc. Trans, y^,, 634. 



Jacobson. 1892. Zeit. fiir physiol. Chem. 16, 340. 



KjELDAHL. 1879. Meddelelser f ra Carlsberg Labor. 1 , 1 2 1 . 



Lintner and Dull. 1893. Ber. d. chem. Gesell. 26, 2533. 



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organismen. 

 Linz. 1896. Jahrb. f. wiss. Bot. 29, 267. 

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LECTURE XIII 

 THE CONVERSION OF THE PRODUCTS OF ASSIMILATION. II 



DISSOLUTION OF THE REMAINING RESERVES IN SEEDS 

 OTHER STOREHOUSES OF RESERVES 



In the course of their researches on starch dissolution in germinating barley. 

 Brown and Morris (1890) found that the cell-walls of the endosperm were 

 also dissolved during germination. The cell-walls of the endosperm of barley are 

 relatively thin, and hence the sugar resulting from their dissolution cannot 

 play any very essential part in the nutrition of the seedling. Probably the 

 significance of the absorption of the cell-walls in this case lies merely in the fact 

 that the other enzymes are thus enabled to enter the cells more readily. The 

 walls of the endosperm cells of other seeds, on the contrary, are remarkably 

 thick, as, for example, in palms and many other Monocotyledons, and here also 

 a dissolution of the cell-walls takes place in germination, so that it is quite legiti- 

 mate to consider the materials of which they are composed as reserves, par- 

 ticularly as other carbohydrates are absent or present only in small quantity. 

 The chemical composition of the ceU-wall is still imperfectly known. At least 

 two groups of substances take part in its formation — pectins and celluloses. The 

 former of these we need not discuss at present since the most divergent views 

 are held as to their chemical characters (Schroder, 1901 [compare Czapek, 

 Biochemie, I, 545]). The celluloses on treatment with acids give rise by hydro- 

 lysis to various types of sugar, dextrose, mannose, galactose, and, following 

 E. Schulze (1890-92), we may regard them as anhydrides of these hexoses as 

 well as of certain pentoses (arabinose and xylose). The cell- wall only rarely 

 consists of a single chemical compound ; in most cases it is formed of a mixture 

 of several. Such celluloses are deposited as reserves in seeds especially, giving 



