12 PHYSIOLOGY. 



warm the slip gently, the movement becomes normal again. We 

 may now apply here the usual tests for protoplasm. The result 

 is the same as in the former cases. 



26. Protoplasm occurs in the living parts of all plants. 

 In these plants rep resenting such widely different groups, we find 

 a substance which is essentially alike in all. Though its arrange- 

 ment in the cell or plant body may differ in the different plants 

 or in different parts of the same plant, its general appearance 

 is the same. Though in the different plants it presents, while 

 alive, varying phenomena, as regards mobility, yet when killed 

 and subjected to well known reagents the reaction is in general 

 identical. Knowing by the experience of various investigators 

 that protoplasm exhibits these reactions under given conditions, 

 we have demonstrated to our satisfaction that we have seen proto 

 plasm in the simple alga, spirogyra, in the common mould, 

 mucor, in the more complex stonewort, nitella, and in the cells 

 of tissues of the highest plants. 



27. By this simple process of induction of these facts concerning 

 this substance in these different plants, we have learned an im- 

 portant method in science study. Though these facts and deduc- 

 tions are well known, the repetition of the methods by which they 

 are obtained on the part of each student helps to form habits of 

 scientific carefulness and patience, and trains the mind to logical 

 processes in the search for knowledge. 



28. While we have by no means exhausted the study of protoplasm, we can, 

 from this study, draw certain conclusions as to its occurrence and appearance 

 in plants. Protoplasm is found in the living and growing parts of all plants. 

 It is a semi-fluid, or slimy, granular, substance ; in some plants, or parts of 

 plants, the protoplasm exhibits a streaming or gliding movement of the gran- 

 ules. It is irritable. In the living condition it resists more or less for some 

 time the absorption of certain coloring substances. The water may be with- 

 drawn by glycerine. The protoplasm may be killed by alcohol. When 

 treated with iodine it becomes a yellowish-brown color. 



Note. In some plants, like elodea for example, it has been found that 

 the streaming of the protoplasm is often induced by some injury or stimu- 

 lus, while in the normal condition the protoplasm does not move. 



