16 



in 2 liters of distilled water, to which were added only 0.2 per mille 

 calcium nitrate and 0.02 per mille ammonium sulphate. When they 

 were placed in this very imperfect solution, the filaments contained 

 in all probability some stored-up mineral matter, hence a moderate 

 further growth of the cells was not surprising. Besides, mineral matter 

 of some cells which died gradually may have been absorbed by the 

 living ones. The cells did not increase by cell division, however, but 

 merely enlarged. After standing six weeks the chlorophyll bodies had 

 assumed a yellow color. The liquid, with the filaments, after the addi- 

 tion of 0.02 per mille ferrous sulphate, was now divided into two por- 

 tions, and 0.5 per mille secondary sodium phosphate was added to one 

 of them. After five days a very striking difference was noticed, the 

 normal green reappearing only in the latter case, which proved that 

 phosphoric acid is an essential factor for the i^roduction of chlorophyll. 

 Stoklasa also has observed the necessity of phosphoric acid for the pro- 

 duction of the chlorophyll green, and finally Macchiata^ inferred from 

 his experiments that plants may become chlorotic not only from a defi- 

 ciency of iron, but also from lack of other mineral nutrients. Indeed, 

 cases exist in which it is the deficiency of magnesia which causes this 

 phenomenon (p. 49). Magnesia appears to form a constituent of the 

 crystallized chlorophyllan of Ho'ppe, which, however, has recently been 

 declared a mixture^ which contains 1.72 per cent ash, of which 1.38 parts 

 are phosphoric acid (mentioned above) and 0.34 magnesia (Hoppe). 



An interesting fact observed by ZimmermannMs that the chloroplasts 

 in chlorotic leaves are smaller than in normal leaves, and appear to be 

 incapable of forming starch from sugar. Different from chlorosis is 

 the albinism of plants. Here the leucoplasts have so far degenerated 

 that they become incapable of producing the green color even when 

 all the necessar}^ mineral nutrients are present. Although incapable 

 of forming carbohydrates from carbonic acid, however, they often form 

 starch from sugar.^ 



FERTLLIZINO EFFECT OF IRON SALTS. 



It is to be expected that a moderate manuring with iron salts would 

 prove beneficial for plants grown on soil deficient in iron. Bracci^ 

 mixed 1 part of ferrous sulphate with 20 parts of silt and applied this 

 mixture to soil in which oats and wheat were grown, and as a result 

 the grain ripened several days earlier and the yields of straw and 

 grain were increased. Spraying with ferrous sulphate is also said to 

 produce favorable results. Yille applied a 2 i^er cent solution to 

 young apple and pear fruits,^ and thus not only hastened the ripening 



iBot. Jaliresber., 1888, p. 20. 



- Compare also the recent publications of Scliunk and Marchlewski, 

 ^Zimmernianu, Beitriige zur Morph., etc., Heft II; Sapoznikoff, Bot. C, 1889, p. 321. 

 •*Bot. Jahresber., 1883, p. 43. 



'"'Ibid, p. 14. Other reports, however, mention an injurious actiou of a 1 per cent 

 solution upon potato plants. 



