12 COLLEGE BOTANY 



Protoplasm. After years of study, accompanied by improve- 

 ments in the microscope, some of these early workers recognized 

 that growing cells were filled with a living substance which was 

 evidently the most important part. The demonstration that this 

 substance was the essential factor in the cell was accomplished 

 by Schleiden (Fig. 3) about 1838. In the following year the 

 same thing was demonstrated for animals by Schwann. In 1855 

 linger called attention to the great similarity of this substance 

 in the plant and animal cells. This substance was described 

 under many names, but is now very generally known as proto- 

 plasm, a name first used by von Mohl (Fig. 4) about 1840. It 

 isi now very generally recognized that protoplasm is the living 

 part of the organism, whether it be plant or animal, and that the 

 protoplasm of the plant and animal are indistinguishable by any 

 known methods. The term " protoplasm " is from the two Greek 

 words protos, meaning " first," and plasma,, meaning " formed " 

 or " created," and refers to the beginning of life. 



The meaning of the word " cell " has changed with our ad- 

 vance in knowledge, but its use is so general that it is very diffi- 

 cult to substitute another term with a more definite meaning. 

 Some workers prefer to use the word " protoplast " for the cell 

 wall and contents, while others use the word cell in referring to 

 the cell wall and " protoplast " in referring to the living proto- 

 plasmic contents. 



Protoplasm is a semi-fluid, albuminous substance in which 

 life makes itself manifest. It is more nearly like the white of 

 an egg than any other *substance with which we can compare it. 

 It is difficult to give a scientific definition of life, but the dis- 

 tinctive characters of a living organism are: (a.) complex chemi- 

 cal composition; (&) metabolic action, i.e., the power of change 



