586 TRA NSL OCA TION 



fruits and seeds may be formed. Ash constituents are, however, usually 

 absorbed from the soil up to the last stages of ripening, although finally 

 only in very minute amounts. Cases have been observed, however, in 

 which towards the end of ripening the total percentage of ash underwent 

 no further increase or even decreased. The latter may also occur in 

 certain organs from which ash constituents are withdrawn for storage, and 

 since the different inorganic salts are unequally concerned in the various 

 processes of constructive metabolism, it is only to be expected that the 

 amounts of each salt absorbed from without should undergo marked 

 fluctuations during the progress of development. 



Both the concentration and the composition of the nutrient solution 

 are of great importance, and any deficiency of such elements as phos- 

 phorus or potassium, &c., causes the growing parts to withdraw them 

 from the older organs and hence induces the premature death of the 

 latter (Sect. 93). An abundant supply, however, not only prevents such 

 exhaustion, but also suppresses to a certain extent the removal of the 

 substances in question from the storage receptacles (Sect. 93), while at 

 the same time its consumption rises slightly above the normal. Moreover 

 when the roots are supplied with concentrated solutions of inorganic salts, 

 the transpiration current may produce so marked an accumulation of these 

 in the leaves that saline efflorescences form upon them (Sect. 23), and in this 

 way a portion of the superfluous salts is removed. Similarly an excretion 

 of saline substances is exhibited when a root-system is removed from 

 a normal or concentrated nutrient solution to a very dilute one. 



Micro-chemical methods have been employed, more especially by Schimper 

 (Bot, Zeitung, 1885, p. 756 ; Flora, 1890, p. 211), for the detection of ash constituents, 

 but Pfeffer (i. Aufl., Bd. I, p. 330) was perhaps the first to show that a salt might 

 be traced by such means. Macro-chemical researches have for the most part been 

 made in connexion with studies upon the accumulation and distribution of organic 

 substances, and such are quoted in Sect. 109. A large part of the literature is 

 mentioned in E. Wolff's Aschenanalysen, 1871 and 1880. In addition, the following 

 works may be mentioned: Arendt, Wachsthum d. Haferpflanze, 1859; Fittbogen, 

 Versuchsst., 1864, Bd. vi, p. 474, and 1870, Bd. xin, p. 100; Pierre, Rech. s. 1. 

 de"v. du ble, 1866; Knop u. Dworzak, Ber. d. Sachs. Ges. d. Wiss., 1875, P- 7^ ; 

 Kreusler, Landw. Jahrb., 1878, Bd. vn, p. 548; Pott, Versuchsst., 1880, Bd. xxv, 

 p. 95; Weiss, ibid., 1880, Bd. xxvi, p. 191 ; Berthelot et St. Andre", Ann. d. chim. 

 et d. phys., 1883, vi. ser., T. v, p. 385 ; Compt. rend., 1891, T. cxn, pp. 122, &c. 



