INTRODUCTION TO PLANTS 197 



answered riddle of life. We do know something about 

 the chemical composition of protoplasm. We know 

 that it is a very complex compound ; that is, it contains 

 many elements. The chief elements are carbon, hydro- 

 gen, oxygen, and nitrogen. Sulphur, phosphorus, iron, 

 potassium, calcium, silicon, and minute quantities of 

 other elements are also found in its composition. 



Properties of protoplasm. Although the living mat- 

 ter of which both plants and animals are composed is 

 almost impossible of correct analysis, we do know that 

 it possesses certain properties which inorganic matter 

 does not possess. These properties are as follows: 



1. Protoplasm grows. It has the wonderful power 

 of taking in food material and then changing it from 

 a non-living substance into living protoplasm. 



2. Protoplasm breathes. It can take in oxygen with 

 which it unites to produce the heat and energy necessary 

 for movement and other activities. 



3. Protoplasm can rid itself of waste materials. 

 Substances, which are of no use to them, collect in 

 organisms, and are, in turn, thrown off. 



4. It is sensitive to influences, or stimulations, from 

 without its own substances. Light, heat, electricity, 

 and other stimuli Avill cause protoplasm to move. 



.I. Protoplasm can reproduce itself. Cells can divide 

 and form other cells. Plants are constantly appearing 

 to take the place of those that die. 



Comparison of plants and animals. From observa- 

 tions, we are all familiar with many living organisms. 



