IRON COMPOUNDS IN ANIMAL AND VEGETABLE CELLS. 177 
forced, more than ever, to depend on micro-chemical methods 
to determine the relations of assimilated iron to the cell. 
Objections may be urged against these methods also, based 
chiefly on the facts that iron, free or combined, contaminates 
everything, so to speak, and that what is shown to occur in 
dead chromatin may not be present in the living compound ; 
but these objections at once lose their force when the methods 
are applied with all due care accompanied by such control 
experiments as the conditions may suggest. 
I have in my former communication made reference to the 
investigations of Bunge and Zaleski upon iron-holding nucleins. 
Since 1891 four other investigators have published observations 
on the occurrence of iron in organic compounds. 
Molisch! endeavoured to determine the relations of iron in 
the vegetable cell by means of concentrated aqueous solutions 
of potash. He found that when vegetable tissues were 
immersed in this reagent for a day or longer, they gave a 
reaction for iron not at all obtainable in the fresh tissues, and 
he explained the result as due to the removal of the iron from 
a firmly combined (‘ maskirt ” ) condition to that in which 
it is readily detectable by ordinary reagents. The firmly com- 
bined iron, as shown by this method, was sometimes in the 
cell wall, sometimes in the cell contents, and sometimes again 
in both. His results do not call for a fuller description than 
this, since in a later publication? he has stated that his 
solutions of potash were not free from iron, and he has con- 
sequently withdrawn all the conclusions which he previously 
based on the results obtained with this reagent. 
Petit,? in investigating the occurrence of iron in barley, 
employed Bunge’s method to separate the inorganic and 
albuminate from the organic iron, using for that purpose a 
1 per cent. solution of hydrochloric acid in absolute alcohol. 
1 ¢Die Pflanze in ihren Beziehungen zum Hisen,’ Jena, 1892. 
2  Bemerkung iiber den Nachweis von maskirterm Hisen,” ‘ Berichte der 
deutschen bot. Gesell.,’ vol. xi, 1893, p. 73. 
3 «Distribution et état du fer dans l’orge,” ‘Comptes Rendus,’ vol, exv, 
p. 246, 1892, 
