PLANT-LIFE. 



CHAPTER I. 



MICROSCOPIC PLANTS. 



NOT the least among the discoveries which we owe 

 to the microscope is the existence of an extensive, 

 though exceedingly minute, world of animal and 

 plant life. No matter where we look, we shall find 

 members of this hitherto invisible world absolutely 

 swarming around us. The very air we breathe is 

 filled with minute forms of life ; and in the water we 

 drink we are certain to find many of them, unless it 

 has been boiled or filtered. Any sweet fluid which 

 has been exposed to ;the air for a few hours will teem 

 with them ; so will water in which any vegetable or 

 animal matter has been infused. Some are so ex- 

 ceedingly small that 20,000 of them placed side by 

 side would not cover the length of an inch. Very 

 expensive and finely- adjusted instruments are, of 

 course, required to enable us to see organisms so 

 extremely minute ; but there are hundreds of inter- 

 esting forms which may be clearly seen by simpler 

 and less expensive instruments. One of the best 



