I02 METABOLISM 



so-called ' Thomas-slag-powder ', the plant is easily in a position to take up 

 the necessary phosphoric acid. This mention of cainite and Thomas-slag- 

 powder by no means exhausts the artificial manures used by agriculturalists 

 but to give further detail would take us too far ; reference must be made for 

 such information to agricultural literature, e. g. Ad. Mayer, Agricultural 

 Chemistry, 1895. 



Bibliography to Lecture VIII. 



CORRENS. 1896. Bot. Ztg. 54, 21. 



CzAPEK. 1896. Jahrb. f. wiss. Bot. 29, 321. 



Ebermayer. 1882. Physiol. Chemie d. Pflanzen. Berlin. 



Engler. 1879-82, Versuch einer Entwickelungsgesch. d. Pflanzenwelt. Leipzig. 



Engler, Arnold. 1901. Ber. Schweiz. bot. Gesell. 11, 23 (Bot. Centrbl. 89, 269). 



Fliche and Grandeau. 1873. Annales d. chim. et d. phys. IV, 2. 



Grabner. 1 90 1. Die Heide Norddeutschlands. Leipzig. 



HdvELER. 1892. Jahrb. f. wiss. Bot. 24, 294. 



Knop. 1868. Der Kreislauf des Stoffes. Leipzig. 



Kny. 1898. Ber. d. bot. Gesell. 16, 216. 



LiEBiG. 1840. Die Chemie in ihrer Anwendung auf Agrikultur, 7th ed., 1862. 



Mayer, Ad. 1895. Lehrbuchder Agrikulturchemie, 4th ed., II, i. Bodenkunde. 



Heidelberg. 

 Nageli. 1865. Sitzungsber. Munch. Akad. (Bot. Mitteilungen, 2, i). 

 NoBBE. 1862. Versuchsstationen, 4, 217 ; 1868, ibid. 10, 94. 

 Ohlmann. 1898. Veg. Fortpfl. d. Sphagnaceen nebst ihrem Verb, gegen Kalk. 



Diss. Freiburg (Schweiz). Braunschweig. 

 Peters, i860. Versuchsstationen, 2, 135. 



Ram ANN. 1893. Forstliche Bodenkunde u. Standortslehre. Berlin. 

 Roux. 1900. Traite des rapports des plantes avec le sol. Montpellier. 

 Sachs. 1865. Handbuch d. Experimental-Physiologic. Leipzig. 

 Sachs. 1892. Flora, 75, 171. 



ScHiMPER. 1898. Pflanzengeographie auf physiolog. Grundlage. Jena. 

 Thurmann. 1849. Essai de phytostatique appl. a la chaine du Jura. 

 Treub. 1888. Annales Jard. bot. Buitenzorg. 



Vallot. 1883. Rech. physico-chimiques s. la terre vegetale. Paris. 

 WoLLNY. 1897. Zersetzung d. organischen Stoffe u. d. Humusbildungen. 



Heidelberg. 

 WoLLNY. 1898. Forschungen a. d. Geb. d. Agrikulturphysik, 20, 133. 



LECTURE IX 

 THE ASSIMILATION OF CARBON BY AUTOTROPHIC PLANTS. I 



Green plants grown in nutritive solutions show a marked increase in dry 

 weight (p. 82), but analysis of the dry substance of such plants shows that the 

 predominant constituent is not the mineral matter absorbed from the solution, 

 but carbon, of which, as a matter of fact, one^half of the dry weight consists. 

 Carbon occurs as a component of nearly everjrcompound found In the plant, 

 and the number of these compounds depends chiefly on the fact that carbon 

 is able to unite with other elements in endlessly variable proportions. In one 

 sense we may look on carbon as the most important material in plant nutrition, 

 although it must be remembered that the minerals are every whit as essential 

 as the carbon. Under these circumstances it may at first sight appear extra- 

 ordinary that we have not introduced carbon into our culture solutions, or 

 at least have not done so intentionally. 



When we inquire whence plants obtain their carbon, we discover that the 

 uniformity of method which prevails among them in regard to the mode of 

 absorption of the constituents of the ash does not hold good here ; there are 

 fundamental differences between different types of plant life in this respect, 

 some absorbing carbon in the inorganic form and transforming it into organic 

 compounds, others making use of carbon solely in the organic form. The 



