[59] Organisms of this kind have been investigated among others by Heraüs, Hueppe, and E. Wollny. According to the two first-mentioned investigators, certain colourless bacteria effect the formation in the absence of light from humus and carbonates a body resembling in its nature cellulose.
[60] Investigated by Springer, Gayon and Dupetit, Dehérain, and Marguenne.
APPENDIX TO CHAPTER I.
NOTE I. (p. 68).
The following determinations by Schübler show the absorptive power of different kinds of soil-substances. These were obtained by soaking weighed quantities of the soil in water, and allowing the excess of liquid to drain away, and weighing the wet earth.
| Per cent of water absorbed by 100 parts of earth. | |
| Siliceous sand | 25 |
| Gypsum | 27 |
| Calcareous sand | 29 |
| Sandy clay | 40 |
| Strong clay | 50 |
| Arable soil | 52 |
| Fine calcareous | 85 |
| Garden-earth | 89 |
| Humus | 190 |
It has been calculated that the absorptive power of a mixture of different substances is not simply equal to the sum of their separate ingredients.
NOTE II. (p. 74).