160 PLANT PHYSIOLOGY 



lipoids, which contain both nitrogen and fatty acids, perhaps play 

 an important role in bringing about the rapid changes so character- 

 istic of the cell. 



5. It has been proposed that lipoids are an intermediate product 

 between fats and proteins. The presence of the fatty acid from the 

 fats, and of choline and other nitrogenous compounds from protein 

 decomposition lends a possibility to this idea. Fats develop in 

 cheese, but according to Nierenstein (1911) such fats come from 

 cholesterol and not from the proteins. 



6. The view has been advanced by Korsakova (1910) and others 

 that lipoids are concerned with the formation of enzymes, especially 

 the proteases, and initiate the changes which lead to the formation 

 of the enzymes from the zymogens (enzyme formers). 



7. Palladin (1910) believed that respiration was dependent upon 

 lipoids. When wheat seedlings were treated with various lipoid 

 solvents, the greater the amount of lipoid extracted the less carbon 

 dioxide was formed. 



These are some of the views concerning lipoids to be found in 

 the literature, but their real function and importance is one of 

 the matters which wait upon further research for their ultimate 

 solution. 



QUESTIONS 



1 . What is an ester? saponification? 



2. Why are fats so important in the conduct of war? 



3. What is the difference between a saturated and an unsaturated com- 

 pound? Give illustrations not discussed in the text. 



4. Some trees are called "fat" trees and some "starch" trees. Give ex- 

 amples and explain the difference. 



5: Which is the more concentrated food, — fat or sugar? Explain. 

 6. Which is the more quickly available? Why? 



REFERENCES 



MacDougal, D. T— The probable action of lipoids on growth.— Proc. Am. 



Phil. Soc, $1:33, 1922. 

 Priestley, J. — The fundamental fat metabolism of the plant. New Phyt., 



23:1, 1924. 

 Tuttle, G. — Induced changes in reserve materials in evergreen herbaceous 



leaves. Ann. Bot., 33:201, 1919. 

 Wiztemann, E. — The law of probability applied to the formation of fats from 



carbohydrates. J. Phys. Chem., 25:55, 1921. 



