12 PHYSIOLOGICAL ROLE OB' MINERAL NUTRIENTS. 



more water and also generally more ash for the dry matter than do 

 the leaves of trees in which transpiration goes on more slowl}', such 

 as (Jin reus, Fagiis, and the common kinds of Pinus. While leaves of 

 Acer show 7 to 9 per cent of ash and those of Salix -1 to 6 per cent, 

 the leaves of Pi mix yiontana and P. austriaca show only 0.58 per cent 

 and 0.74 per cent, respectively (Ebermayer). There is more ash in 

 the leaves than in the roots or stems, more in the roots and stems than 

 in the seeds, and more in the seeds than in the wood. 



MINERAL COMPOUNDS FOUND IN ORGANISMS. 



The mineral compounds chiefly found in living organisms contain 

 phosphates, sulphates, carbonates, and chlorids, magnesia, lime, soda, 

 potash, iron compounds, and silica. Small quantities of iodin and 

 fluorin compounds are also found in both kingdoms. Bromin com- 

 pounds occur in seaweeds. Occasionally there are present in plants 

 small quantities of titanic and boric 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 aglse 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 Risse to be incapable of replacing the iron in plants and was 

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

 Bertfand, a frequent constituent of the vegetable oxidizing enzymes. 6 

 Manganese also was found in the animal bod}*. The nitrates and 

 sulphates present in plants serve chiefly as sources of nitrogen and 

 sulphur for protein formation, and consequently do not require 

 further discussion. As physiological elements these must be desig- 

 nated: Potassium, sodium, calcium, magnesium, iron, phosphorus, 



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

 also traces of vanadin, rubidium, and caesium compounds. Wait found 0.31 per cent 

 titanic acid in the ash 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. Recently traces of 

 arsenic were observed in normal animals, especially in the epidermis, by Gautier and 

 Bertrand. ( lopper has been found in the liver of Cephalopoda by Frederique and by 

 Henze, further in plant ash by MacDougal, lleckel, and others, while Demaicav 

 has identified vanadium, molybdenum, and chromium compounds in the ash of cer- 

 tain plants. Arabis halleri (Fricke) and Viola calaminaris thrive on soils rich in zinc, 

 while Amorpha caneseens grows well on a lead soil. 



''According to Lepinois, iron can replace manganese in the oxidizing enzymes. 

 Woods lias further observed the presence of oxidase in plants grown in the absence 

 of manganese. ( >xidases, however, act more powerfully in the presence of manganese 

 than of iron (Bertrand). 



