THE ASH OF PLANTS. 219 



ripe, well-developed buckwheat seeds in chlorine-free 

 water-cultures, while in the same solutions, with addition 

 of chlorides, other buckwheat plants remained sterile, 

 the flowers withering without setting seed. Knop states 

 that in other trials maize and bean plants grew better 

 without than with chlorides. In either case starch did 

 not accumulate in the stem or leaves of maize, while all 

 the organs of the bean were overloaded with starch both 

 in presence and absence of chlorides. 



The experiments of Nobbe and Leydhecker are very 

 circumstantially described and have been confirmed by 

 the later work of Nobbe, Schroder, and Erdmann ( Vs 

 St., XIII, pp. 302-6). See p. 196. 



Iron. We are in possession of some interesting facts, 

 which throw light upon the function of this metal in the 

 plant. In case of the deficiency of iron, foliage loses its 

 natural green color, and becomes pale or white even in 

 the full sunshine. In absence of iron a plant may un- 

 fold its buds at the expense of already organized matters, 

 as a potato-sprout lengthens in a dark cellar, or in the 

 manner of fungi and white vegetable parasites ; but the 

 leaves thus developed are incapable of assimilating carbon, 

 and actual growth or increase of total weight is impossi- 

 ble. Sulm-Horstmar showed (1849) that plants which 

 grow in soils or media destitute of iron are very pale in 

 color, and that addition of iron-salts very speedily gives 

 them a healthy green. Sachs found that maize-seed- 

 lings, vegetating in solutions free from iron, had their 

 first three or four leaves green ; several following were 

 white at the base, the tips being green, and afterward 

 perfectly white leaves unfolded. On adding a few drops 

 of sulphate or chloride of iron to the nourishing medium, 

 the foliage was plainly altered within twenty-four hours, 

 and in three to four days the plant acquired a deep, lively 

 green. Being afterwards transferred to a solution desti- 

 tute of iron, perfectly white leaves were again developed, 



