9 



oxalate in certain leaves against snails; the incrustations of leaves and 

 entire plants (Chara) by caloiiim carbonate; the lime shells of Fotami- 

 nifera, certain worms, mollusca, and eggs of birds; the silica shells of 

 diatoms; and the secretion of dilute sulphuric acid by certain Gastro- 

 poda, as Dolium, Cassis, etc. Finally, mineral matter may be an object 

 of adaptation, as the salts in sea water is for marine animals. How- 

 ever, in this bulletin the physiological role alone is the subject of 

 discussion. 



MINERAL COMPOUNDS FOUND IN ORGANISMS. 



The mineral compounds usually found in living organisms are 

 phosphates, sulphates, carbonates, chlorids, silica, iron compounds, 

 magnesia, lime, soda, and potassa; while in plants nitrates, manganic 

 compounds, and minute quantities of fluorides also often occur. Small 

 quantities of iodine compounds are found in both kingdoms. Bromine 

 compounds occur in sea weeds. Occasionally there are present in 

 plants small (juantities of titanic and boracic acids, lithia, and alumina, 

 and of the oxids of lead, zinc, and copper." Sodium salts are not 

 necessary for physiological uses of plants, but are for those of animals. 

 Calcium salts are of great importance for plants and animals, only the 

 lower fungi and lower alga? being able to do without them. Magnesium 

 and potassium salts, however, can not be dispensed with by any living 

 cell any more than can phosphoric acid. Manganese, which was shown 

 by Eisse to be incapable of replacing the iron in plants and was believed 

 to be entirely useless, forms, according to recent researches of Bertrand, 

 an essential constituent of the vegetable oxidizing euzynis, and hence 

 may be also of physiological interest.- The nitrates and sulphates 

 present in plants serve, in regard to their acids, chiefly as sources of 

 nitrogen and sulphur for protein formation, and consequently do not 

 require further discussion. As physiological elements these must be 

 designated potassium, sodium, calcium, magnesium, iron, phosphorus, 

 chlorine, iodine, carbon, hydrogen, nitrogen, oxygen, and sulphur. 



GENERAL VALUE OF CERTAIN MINERAL SALTS. 



Mineral salts have not only to perform ecological as well as specific 

 chemical functions, but also seem to contribute directly to the mainte- 

 nance of the continuance of the living condition of the protoplasm. A 

 most striking instance of this is the rapid dying of infusoria in distilled 

 water. The writer entertained for a time the supposition that this 



'Lippmann observed in the sugar beet not only boric acid and copper oxid, but also 

 traces of vanadin and caesium compounds (Bot. Jabrb., 1888). Wait found 0.31 per 

 cent titanic acid in the asli of oak wood, 0.11 per cent in the ash of apples, and traces 

 of it in bones and meat, and Dunnington found it in many soils. 



^According to Lepinois, iron can replace manganese in this regard, and the forma- 

 tion of oxidase in plants raised in the absence of manganese was further observed 

 by Albert F. Woods. 



