The Typical Cellulose and the Cellulose Group 73 



posed, i.e. of the bacteria enveloped in a * collecting medium ' 

 of cellulose. The proportion of cellulose formed, to the soluble 

 carbohydrate disappearing, is highest in the case of levulose. 



It is remarkable that the cellulose formed, when hydrolysed 

 by sulphuric acid, gives a dextro-rotary sugar. The organism 

 also has the power of determining the oxidation of ethyl alcohol 

 to acetic acid, and of dextrose to gluconic acid. But its 

 characteristic property is that of the building up of cellulose 

 from the carbohydrates of lowest molecular weight, whence its 

 descriptive name Bacterium Xylinum. 



The synthesis of cellulose is a problem involving the whole ques- 

 tion of * assimilation ' of ' organic ' substance by the plant. It has 

 been held generally by physiologists for a long time that starch 

 is the first visible product of assimilation in the plant cell. On this 

 subject the student should read Sachs's classic work on * Vegetable 

 Physiology,' the investigations of this observer having contributed 

 in a very important degree to the establishment of the above view. 

 A priori, perhaps, it appears somewhat singular that the plant 

 should invariably proceed by way of starch to the elaboration of its 

 permanent tissue. Recent researches of Horace Brown and G. H. 

 Morris (J. Chem. Soc. 1893, 604) throw doubt upon the con- 

 clusion from the experimental side. Again, we recommend to the 

 student a careful study of the work of these authors, not merely for 

 the results obtained and described, but for the excellent plan of the 

 investigations. We give a few of the main conclusions in which these 

 investigations issued. * It is perfectly true, as pointed out by 

 Sachs, that starch is the first -visible product of assimilation ; yet 

 there can be little doubt (as was, in fact, anticipated by Sachs him- 

 self) that between the inorganic substances entering into the first 

 chemical process of assimilation and the starch there is a whole 

 series of substances of the sugar class, and that it is from the last 

 members of this series that the chloroplasts, under normal con- 

 ditions, elaborate their starch. Both under the natural conditions 

 of assimilation and the artificial conditions of nutrition with sugar 

 solutions the chloroplasts form their included starch from ante- 

 cedent sugar.' 



Observations on the secretion of diastase by the leaves of 



