72 



PLANT CELLS 



modium of this species are probably almost entirely foods. The inorganic com- 

 pounds ("mineral matter") in plant cells are chiefly the phosphates, chlorides, 

 sulfates, and carbonates of magnesium, potassium, sodium, and calcium. 



table 12 analysis of the plasmodium of a myxomycete resembling fuligo varians. 



(data of lepeschkin, 1923) 



A. Water soluble substances, chiefly from vacuoles: 



Monosaccharides 



Proteins 



Amino acids, asparagine, etc 



B. Insoluble organic substances, principally constituents of the protoplasm: 



Nucleo-proteins 



Nucleic acids 



Globulin 



Lipo-proteins 



Neutral fats 



Phytosterol 



Phosphatides 



Other organic matter 



C. Mineral matter, about half water soluble 



Percentage of 



dry weight 



14.2 

 2 . 2 



243 



3 

 5 

 5 



4 



6 



3 

 I 



3 



4.4 



An analysis such as that presented in Table 12 is not without value 

 inasmuch as it furnishes some information regarding the kinds and propor- 

 tions of the compounds present in protoplasm. It supplies no more informa- 

 tion regarding the organizatw?i of protoplasm, however, than a chemical 

 analysis of the ground up debris of a wrecked house would furnish regarding 

 the structure of that house. This point is worthy of emphasis, since with 

 the progress of biology it becomes clearer and clearer that the properties of 

 protoplasm are as much a function of its physiochemical organization as of 

 the specific kinds of compounds present. Although we commonly refer to 

 "protoplasm" as the essential constituent of all living cells, it is evident that 

 there are at least as many different varieties of protoplasm as there are species 

 of plants and animals. All of them, however, are dynamic systems composed 

 of the same types of compounds, and all of them possess a colloidal organiza- 

 tion of a complex type. 



The Physical Properties of Cytoplasm.— Although it is not possible to 

 explain adequately the mechanisms responsible for the physiological activities 

 of cytoplasm it is possible to study the behavior of cytoplasm under various 



