PILAN ¥.-LA FE. 
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 
A 
