THE CONDUCTION OF WATER. II 77 



GODLEWSKI. 1884. Jahrb. f. wiss. Bot. 15,602. 



Hales. 1748. Statik der Gewachse. Halle. 



Hartig, R. 1882. Unters. aus d. forstbot. Instit. Miinchen, 2, i. 



Hartig, R. 1883. Ibid. 3, 71. 



Hartig, Th. 1861. Bot. Ztg. 19, 22. 



HoFMEisTER. 1 862. Flora, 45, 97. 



HoHNEL. 1879. Jahrb. f. wiss. Bot. 12, 47. 



Janse. 1887. Jahrb. f. wiss. Bot. 18, i. 



McNab. 1 87 1. Trans. Bot. Soc. Edinburgh, 11, 45 



Nageli. 1866. Sitzungsber. Bayer. Akad. d. wiss. Bot., Mitt. 2, 369 and 429. 



Nernst. 1900. Theoret. Chemie, 3rd ed., p. 165. 



Noll. 1897. Sitzungsber. Niederrhein. Gesell., November. 



Pappenheim. 1892. Bot. Centralb. 49, i. 



Pfeffer. 1892. Stud. z. Energetik. (Abh. Kgl. Gesell. d. "Wiss. Leipzig, 18.) 



Reinganum. 1896. Annalen d. Physik (Wiedemann), N. F. 59, 764. 



Pfitzer. 1877. Jahrb. wiss. Botan. 11, 177. 



RoTHERT. 1899. Bullet, de I'Acad. de Cracovie, 34. 



Sachs. 1873. Arb. Wiirzburger bot. Inst, i, 288. 



Sachs. 1878. Ibid., 2, 148. 



Sachs. 1879. Ibid., 2, 291. 



ScHWENDENER. 1 882. Die Schutzscheiden. Abh. d. Berl. Akad. (Ges. Abh. 2). 



ScHWENDENER. 1 886. Sitzungsber. Berl. Akad. 561 (Ges. Abh. i, 207). 



ScHWENDENER. 1892. Ibid. 911 (Gcs. Abh. I, 256). 



ScHWENDENER. 1893. Ibid. 835 (Ges. Abh. i, 298). 



Steinbrinck. 1894. Ber. d. bot. Gesell. 12, 120. 



Strasburger. 1 89 1. Bau und Verrichtungen der Leitungsbahnen (Histol. 



Beitr. 3). Jena. 

 Strasburger. 1893. Ueber das Saftsteigen (Histol. Beitr. 5). Jena. 

 Vesque. 1883. Ann. so. nat. 15, 5 

 Westermaier. 1884. Sitzungsber. Berl. Akad. 1105. 

 Wieler. 1888. Jahrb. f. wiss. Bot. 19, 82. 

 WiELER. 1893. Cohn's Beitr. z. Biologie, 6, i. 

 Zimmermann. 1885. Berichte d. bot. Gesell. 3, 290. 



[Many of the questions with which this lecture deals have been discussed by 

 Ewart, 1905 (Phil. Trans. B. 198, 41-85 ; abstracted in Proc. R. S. 74 ; compare 

 Ann. Bot. 443). Into the results of his studies it is unfortunately impossible to go.] 



LECTURE VII 



ASH. I 



All plants contain greater or less quantities of incombustible substances, 

 and small fragments of the cell-wall or starch granules leave behind them, on 

 combustion, demonstrable quantities of ash. The experiences of everyday life 

 confirm this. Every one in days gone by had an opportunity of seeing wood- 

 ash, but, perhaps, this opportunity does not occur quite so frequently in these 

 days of coal consumption ; still cigars are smoked everywhere, and they 

 illustrate the relatively large proportion of ash present in plant organs. No 

 modern investigator has any doubt that all these mineral constituents of the 

 plant must be obtained from without, and in the main from the soil. It is, 

 therefore, most instructive to note that in earlier times this, to us, self-evident 

 fact was thought to require definite proof, and that, even after the establish- 

 ment of the law of the indestructibility of matter, famous academies suggested 

 prize essays with the object of determining whether this law held also for 

 organic nature. For instance, in 1800, the Berlin Academy formulated this 

 question : — 



' By what means are the earthy constituents obtained which, as a result 

 of chemical analysis, are found to be in the various indigenous cereals ? Do 

 they enter these plants in the same form as they are found in them, or are 



