60 MISSOURI BOTANICAL GARDEN. 
not think of what he said. He pictured the peaceful groves, 
orchards and fields of our neighborhood as a scene of 
deadly and unrelenting war. He showed that every worm, 
insect and bird was continually hunting its prey and was in 
turn being hunted by its enemies. It is this wholesale 
butchery which keeps insect pests at bay. Sometimes un- 
usual drought or wet will give certain species an advantage. 
They become numerous, and then their enemies thrive and 
the balance is restored. And he predicted that the horti- 
culturist and farmer would finally take an intelligent hand 
in this war: that they would encourage their insect friends 
in the slaughter of their insect enemies. 
In a former, a pre-scientific time, if crops failed, or the 
plague came, the matter was intellectually disposed of by 
saying that the evil spirit did it or the angel of the Lord 
brought vengeance. Now we hunt for bacteria. This is 
the distinctive feature of science, to seek a rational expla- 
nation of things we do not understand. 
It is a great step to replace the unreasoning fatalism of 
the pilgrim to the shrine of Mecca, by the staining solu- 
tions and the microscope of Koch. The same methods ap- 
plied to the enemies of the horticulturist have produced 
like results. And they will produce yet greater results. 
The number of remedies in reach of the physician con- 
tinually increases. Similarly, the means of warfare against 
your insect enemies must increase. The number of chem- 
ical compounds that may be produced from the known 
chemical elements is too vast for comprehension. The city 
of St. Louis does not contain houses enough to hold the 
books which would contain only the names of the sub- 
stances which can be produced from the known elementary 
substances. If all the scientific men on the earth had 
begun to make and study these substances, with a view of 
finding out what use could be made of them, and had con- 
tinued in ceaseless labor from the dawn of history until the 
present moment, their work would have just begun. They 
