l6o THE ENERGY OF THE LIVING PROTOPLASM. 



can be carried out by every plant-cell, others only by specifically 

 endowed ones, and, while certain compounds are found in all 

 cells, such as carbohydrates, fats, and proteids, others are not of 

 universal occurrence, though still very frequent, as tartrates, 

 succinates, glucosides, resins, tannin. (I) Others, again, are very 

 rare, being either restricted to one family, as quinine or strych- 

 nine, or to a few families, as caffei'n. (2) 



In scrutinising the chemical activity of a plant-cell, we have 

 at first to pay attention to the differentiation of the plasmic 

 contents and the division of chemical labour. The cortical layer 

 of the cytoplasm has not the same function as the inner layer 

 or to no pi 'ast ; the former produces the cellulose-wall from starch 

 or sugar, while the latter restrains noxious substances accumula- 

 ted in the vacuole from returning into the protoplasm. The 

 leiikoplasts form starch from sugar, thereby preventing a higher 

 concentration of the sugar-solution which would to some 

 extent check plasmic activity. The chloroplasts (" chlorophyll- 

 granules"), again, with the aid of ethereal oscillations of a deter- 

 mined wave-length, transform carbonic acid into sugar.' 3 ' The 

 nucleus, finally, is charged with the duty of producing the necessary 

 enzymes ; diastase is required to bring starch into solution for 

 purposes of transportation and transformation, and proteolytic 

 enzymes to utilise aleurone-grains, during the germination process. 



(1) For the chemical relations and full descriptions of tannins see Henry 

 Trimble, The Tannins, Philadelphia, 1894. 



(2) Cf. A. Husemann and A. Hilger, Die Pflanzenstoffe ; also Ed. Schiir, 

 Schweizer Wochenschrift fi'ir Pharmacie, 27, 197. Certain of the accessory com- 

 pounds may still serve some biological purpose as that of attracting insects for fecun- 

 dation, or of protection against fungi and animal parasites, while others are useless 

 by-products and mere excretions. 



(3) Carbonic acid is often called a food for plants, although it is only the material 

 from which plant food (glucose, etc.) is prepared in the chlorophyl-bodies, a logical 

 distinction pointed out by F. Stohmnnn (Z. Biol, 31, 365). In the assimilation of 

 carbonic acid it is generally assumed that formic aldehyde is the first product. This 

 yields, however, upon condensation in solution, as I have shown, not dextrose but 

 other sugars ; moreover, it is poisonous. Therefore, I have added the hypothesis 

 that the formic aldehyde first formed combines with certain hydroxyl-groups in the 

 protoplasm of the chloroplasts, the amido-groups being protected. The condensation 

 taking place afterwards must thus lead always to one and the same configuration of 

 the resulting sugar, since the molecules of formic aldehyde have lost their freedom of 

 motion. Cf. O. Loew, Ber. D. Chem. Ges. 1889, 484 ; also, ibid., 473 and 474. 



