22 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



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 

 addition of 0.02 per mille ferrous sulphate, was now divided into two 

 portions, and 0.5 per mille secondaiy 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 production of chlorophyll. 

 Stoklasa also has observed the necessity of phosphoric acid for the 

 production of the chlorophyll green, and finally Macchiata" inferred 

 from his experiments that plants may become chlorotic not only from 

 a deficiency 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. 58). 



An interesting 1 fact observed by Zimmermann * is that the chloro- 

 plasts 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 degener- 

 ated that they become incapable of producing the green color, even 

 when all the necessary mineral nutrients are present. Although 

 incapable of forming carbohydrates from carbonic acid, however, 

 they often form starch from sugar/ 



FERTILIZING EFFECT OF IRON SALTS. 



It is to be expected that a moderate manuring with iron salts w T ould 

 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. Ville applied a 2 per cent solution to 

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

 process, but also enlarged the size of the fruit. Cugini seeks to explain 

 this on the ground of stimulation of the protoplasm and increased 

 production of chloroplasts in the epidermis. 



ORGANIC COMPOUNDS CONTAINING IRON. 



Haemoglobin is not the only organic iron compound in organisms. 

 Bunge isolated from the yolk of eggs a nuclein-like body, ha?matogen, 



«Bot. Jahresber., 1888, p. 20. 



''Zimmermann, Beitrage zurMorph., etc., Heft If; Sapoznikoff, Bot. C, 1889, p. 821. 

 <■ Bot. Jahresber., 1888, p. 20. 

 ''Bot. Jahresber., 1883, p. 43. 



« Bot. Jahresber., 1883, p. 14. Other reports, however, mention an injurious action 

 of a 1 per cent solution upon potato plants. 



