564 Prof. B. Moore. Presence of Inorganic Iron 



was specially concerned in proving the presence of organic iron in the 

 chromatin of the nucleus and was not searching for iron in the chloroplasts, 

 so that the reference above to the presence of iron in the cyanoplasts of the 

 Cyanophycere is highly interesting to-day. 



Molisch {Joe. cit.) used long immersion in saturated potassium hydrate as a 

 preliminary method for setting free masked iron (i.e. organic iron) in available 

 form for after-detection by potassium ferrocyanide and hydrochloric acid, and 

 in the later testing used very strong hydrochloric acid (10 to 20 per cent.). 

 Such drastic procedures are very dangerous, because the alkali breaks down 

 the delicate chloroplasts, and may also itself contain iron salts in traces ; also 

 in the second place, as pointed out by Quincke,* such strong acid will fairly 

 rapidly set iron free in inorganic or ionic form from the potassium ferro- 

 cyanide reagent, and this ionic iron reacting with the remainder of the reagent 

 will give the Prussian blue colour. Molisch found more iron in the epidermis 

 and fibro-vascular bundles of green leaves than in the green mesophyll, but 

 as he himself admits " the potassium hydrate so disorganises the nucleus and 

 chlorophyll-granules that one can conclude nothing as to the distribution of 

 iron in the cell." 



So far as we have been able to discover there exist no records later than 

 the above in the literature of the subject on the occurrence of iron in the 

 chloroplasts of the green cell, nor any information as to the form in which 

 iron compounds are present. ~No investigations with the iron hematoxylin 

 test of Macallum appear to have been made hitherto upon plants. 



Experimental Methods. 



In carrying out tests for the detection of inorganic iron in the chloroplasts, 

 and in plant tissues generally, two points must be carefully borne in mind, 

 first, the previous preparation of the tissue and its subdivision so that the 

 parts possibly containing iron may be penetrated by the reagents used for the 

 detection, and secondly, that the reagents be applied carefully so that false 

 results are not obtained. Here care must be taken with the concentration of 

 the reagents and the relative periods of time within which positive results 

 are obtained. 



In regard to the preparation of the tissues, if sections are to be cut, care 

 must be taken that this is done with a clean burnished knife. Control 

 experiments show that a clean steel knife leaves no iron on the section. But, 

 in most cases, since the question at issue is not the structural arrangement 

 but rather whether this or that constituent contains iron, it is better to work 

 with finely teased or broken up tissues. For this purpose glass rods drawn 

 * 'Arch. f. Exp. Path. u. Pharm.,' vol. 37, p. 183 (1896). 



