i6o 
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 caffeïn. (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 tonoplast ; 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 
leukoplasts 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. Husernann and A. Hilger , Die Pflanzenstoffe ; also Ed . Schär, 
Schweizer Wochenschrift für Pharmacie, ay, 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. Stohmann (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-gronps 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. 
