CRYPTOGAMS 267 



1. Selective absorption is the ability to take or reject 

 those things which are needed. This is shown in the fact 

 that two plants, as corn and tobacco, growing side by side 

 in the same soil, will take up only those substances needed 

 by each. Again, the leaf takes into its stomata all the sub- 

 stances of the air, but selects only the carbon dioxide for 

 making starch and enough oxygen for respiration, giving 

 back what it rejects into the atmosphere. 



2. Metabolism is the power of protoplasm to utilize the 

 absorbed materials and give off wastes. 



3. Assimilation is the making of more protoplasm out of 

 the substances which have been selected and changed 

 (1 and 2). 



4. Growth. Increase in size and weight naturally results 

 from the increase in the amount of protoplasm (1, 2, and 3). 



5. Excretion. This is the ability to throw off waste 

 matters. This is seen in the excretion of water in transpira- 

 tion, in excretion of oxygen in photosynthesis, and in the 

 excretion of carbon dioxide in respiration of all living things. 



6. Reproduction is shown in the power of plants and ani- 

 mals to propagate their kind. 



7. Automatic movement. Protoplasm is the only form of 

 matter which can move of itself. It can contract, expand, 

 and move about from place to place. This is seen in the 

 streaming of sap, in the change in position of leaves, and 

 in the motions of animals from one place to another. 



8. Irritability. This is the power to respond to outside 

 influences called stimuli. The behavior of tendrils, the 

 phenomena of hydrotropism, heliotropism, and geotropism, 

 all illustrate this property. 



Cells. A unit of protoplasm is called a cell or protoplast. 

 It is the smallest particle of protoplasm that can live alone. 



