Minnesota Plant Life. 485 



Since plants have no nerves by which shocks are transmitted 

 to a central system and thence to every portion of the body, 

 they die much more slowly than do animals. 



Location of the living substance. Only in very lowly crea- 

 tures, such as the slime-moulds, does the greater part of the 

 body consist of living substance. The jelly-like masses de- 

 scribed for such organisms are among the best examples of 

 pure protoplasm. Generally the body of the plant consists, 

 for the most part, of wood, bark, cellulose, starch, oils, water, 

 sugar, ash and a great variety of other compounds manufac- 

 tured at different times by the living substance. One exam- 

 ining a tree or herb in the ordinary way can neither see nor 

 touch any of the living substance, whatever, but must lay his 

 hand upon leaf-skin, cork or some of the various other periph- 

 eral materials of the plant. It is not otherwise if an animal 

 be investigated in like superficial manner. The living sub- 

 stance lies concealed within the walls of the city it has built. 

 To see it and to study it most delicate manipulation is neces- 

 sary. 



Certain portions of plants are transparent and at the same 

 time contain living substance. Sucli areas are favorable for 

 observation. If, for example, some of the hairs that grow 

 along the stem of a tomato-vine are carefully removed, placed 

 in a drop of water and examined under a sufficiently powerful 

 microscope, it will be discovered that they are composed of 

 cylindrical joints. Each joint has a wall transparent as glass, 

 and, within, most of the interior is occupied by water. There 

 is also present, however, a pellucid slime, very conspicuous 

 when once identified. It keeps up a remarkable streaming 

 motion and tiny granules in it are carried along like boats in 

 a rapid current. The direction of the stream changes from 

 time to time. Eddies form in the current. Sometimes the 

 streams flow together from dift'erent parts of the cell interior 

 and a mound of slime is formed. Sometimes the streams fork 

 again and again, making a network within the cell. The mo- 

 tion may cease if the temperature is lo^^ered or raised beyond 

 certain limits. It ceases, also, if the cell becomes dry or if it 

 is exposed to the vapors of ether or chloroform. A slight 

 electric shock stops the movement, but after a time it may 



