§ 1] UPON THE RATE OF GROWTH 327 



dioxide, Spirogyra may form starcli from methylalcohol, for- 

 maldehyd, glycol, methylal, acetylethylesteracetat, acetic acid^ 

 lactic acid, butyric acid, succinic acid, phenol, asparaginic acid, 

 citric acid, acid calcium tartrate, ammonium tartrate, calcium 

 bimalate, glycocoll, tyrosin, leucin, urea, hydantoin, kreatin, 

 and peptones.* Phanerogams form starch from glycerine, cane 

 sugar, levulose, dextrose, lactose, maltose, mannit, dulcit, and 

 lecithin. While daj'light favors assimilation it can be in some 

 cases dispensed with. Thus the potato plant can accumulate 

 starch in the dark when glycerine is used as food. 



An attempt to gain a deeper insight into the conditions of 

 formation of albumen from organic matter has been made by 

 Hanstben ('96), who reared Lemna in solutions of grape sugar 

 or cane sugar, on the one hand, and amids, like asparagin, urea, 

 glycocoll, leucin, alanin, or kreatin, on the other; also on grape 

 sugar and inorganic nitrogenous bodies such as potassium 

 nitrate, sodium nitrate, ammonium sulphide, and ammonium 

 sulphate. As a result of feeding on grape sugar alone at 20° C. 

 during 24 hours, much starch was stored in the cells ; when 

 grape sugar and inorganic nitrogenous bodies were combined 

 little starch and much albumen were produced. Much albumen 

 was also gained when the nutritive solution contained cane 

 sugar and urea, or asparagin and ammonium chloride, or 

 asparagin and ammonium sulphate. The production of albu- 

 men in green plants is favored by nitrogenous organic com- 

 pounds. 



c. Animals. — These organisms are distinguished from the 

 foregoing by an immense requirement of energy for their 

 muscular processes, much of which is continually lost to the 

 organism in the form of motion communicated to the environ- 

 ment. On the other hand, growth is generally slower than in 

 plants. Consequently in animal nutrition thermogenic foods 

 are the more important and the nutritive processes are prevail- 

 ingly exothermic. The plastic processes are the less striking ; 

 nevertheless, it is they which chiefly concern us in our study 

 of growth. 



Among the organic compounds ingested, carbohydrates are 



* The reagents were employed in about 0.1% solution, and whenever acid were 

 neutralized with lime-water. 



