THE ESSENTIAL ELEMENTS 



419 



culture method was resuscitated by Sachs, who succeeded in growing healthy 



plants by alternately transferring them from one solution, containing a portion of 



the ash constituents, to another which contained the remainder, while Knop grew 



plants successfully in a 



single solution containing 



all the essential mineral 



constituents. Numerous 



researches have been per- 



formed in the latter manner, 



and it has been found pos- 



sible to obtain perfectly 



normal growth and de- 



velopment in various higher 



plants, when grown in 



watery culture - solutions, 



although it does not follow' 



that all plants which grow in 



a soil rich in humus can be 



cultivated in this manner, 



for the root-system is under 



much more favourable con- 



ditions in such a soil than 



it is in a watery culture- 



solution l (Sec. 28). 



In Fig. 61 the effects 

 of the absence of iron and 

 potassium are shown (cf. 

 also Fig. 60, p. 397). The 

 glass vessel g contains the 

 nutrient fluid, and the plant 

 is fixed in the median aper- 

 ture of the porcelain lid 

 by means of a halved cork 

 previously soaked in para- 

 fin. Young seedlings are 

 preferably employed and 



trip spprk rn-iv hp Q-prmi 

 tne SeedS may DC germi- 



nated in sawdust, or be- 



tween moist filter-paper, or when all absorption of mineral constituents is to be avoided 



from the commencement, they may be allowed to germinate on gauze netting 



FIG. 61. Water-cultures of Buckwheat. W) without potassium, (.5) in 

 normal nutrient solution, (C) without iron. 



1 Woodward, Phil. Trans., 1699, Vol. xxi, p. 208; Duhamel, Naturgesch. d. Baume, 1765, 

 Bd. II, p. 160; Sachs, Sitzungsb. d. Wien. Akad., 1858, Bd. xxvi, p. 331 ; Yersuchsst., 1860, Bd. II, 

 pp. 22, 224; Knop, ibid., 1861, Bd. Ill, p. 295; Stohmann, Ann. d. Chem. u. Pharm., 1862, 

 Bd. cxxi, p. 314; and numerous works by Nobbe, Wolff, &c., jnentioned in Jahresb. f. Agr.- 

 Chem. for 1861 and following years. 



E e 2 



