FACT AND THEORY 285 



a shift in new environment ; after which we must 

 rebuild our bridges and revise all our maps. 



Since the subject of classification is an impor- 

 tant one; and since I have at times upset some 

 man-made laws or theories it may be well, at this 

 point, to take a bird's-eye glimpse over the maps 

 and charts which have been worked out. 



With a subject in which the bulk of truth is 

 masked in the obscurity of past ages, and with 

 many men of many minds attacking it from 

 many viewpoints, it is only to be expected that 

 there should be differences of opinion. 



But, for the sake of making the explanation 

 clear, we may for the moment overlook minor 

 divergences and view only the main backbone 

 plan which meets with the broadest acceptance. 

 To begin at the beginning, we see first, spread 

 before us, three kingdoms whose boundary lines 

 are well surveyed and whose extent is all-inclu- 

 sive. These are the mineral, the vegetable, and 

 the animal kingdoms. 



Our interest lies now in the vegetable king- 

 dom, which bridges the space between the other 

 two. This kingdom first divides itself into six 

 (perhaps seven) branches, or subkingdoms, 

 called phyla. 



The lowest of these subkingdoms includes only 

 those vegetables of the simplest type which re- 



