. Contributions from the Botanical Laboratory, vol. 7. Botany; Botany. 418 THE AMERICAN NATURALIST [ C-C. HO-C-H HO-C- C-G' Fig. 4. HOHX-C H O I c h-C-CH,OH C-OH H;C-OH c I 0 I c. H c I 0 I c HO-C-H HO-C-hl H-C-CHjOH H C I O M C I 0 I A. Three *'glucose residue" units (one and one half Unks) of a cellulose chain. B. A molecule of cellobiose. a ring—by an oxygen bridge, the bond being between car- bons 1 and 4—is another ring which is the reflected image of the first, that is, it is rotated through 180°. These two units, taken as a pair, constitute one link in the cellulose chain.
. Contributions from the Botanical Laboratory, vol. 7. Botany; Botany. 418 THE AMERICAN NATURALIST [ C-C. HO-C-H HO-C- C-G' Fig. 4. HOHX-C H O I c h-C-CH,OH C-OH H;C-OH c I 0 I c. H c I 0 I c HO-C-H HO-C-hl H-C-CHjOH H C I O M C I 0 I A. Three *'glucose residue" units (one and one half Unks) of a cellulose chain. B. A molecule of cellobiose. a ring—by an oxygen bridge, the bond being between car- bons 1 and 4—is another ring which is the reflected image of the first, that is, it is rotated through 180°. These two units, taken as a pair, constitute one link in the cellulose chain. The structural formula of a link and a half, , of three glucose residues, is given in the accompanying Fig. 4, A. By repeating this link some twenty times (forty glucose residues) we arrive at the structure which constitutes a cellulose chain. This is the nearest ap- proach to that which can be regarded as a cellulose molecule. No. 688] CONTRACTILITY OF PROTOPLASM 419 A moment's study of the formula of a link reveals the fact that it is really the simple sugar, cellobiose, minus water. The structural formula for cellobiose is given in Fig. 4, B. This is a perfectly definite compound of fixed molecular weight. The length of a cellulose chain is not fixed. It is capa- ble, stoichiometrically at least, of reaching any length. One can not, therefore, speak of a cellulose molecule in the strict sense. The molecule as a definite and fixed thing does not exist, that is, its size can not be ascertained with certainty. Sponsler and Dore,^° on the basis of X-ray studies, have reached conclusions which are in certain respects similar to those set forth here. They were among the first X-ray workers to emphasize the long chain structure. The arrangement of the atoms suggested by Sponsler and Dore differs somewhat from that generally held. These investigators regard cellulose as made up of glu- cose units of which the amylene oxide ring formula is in closest agreement with X-ray r
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