FACT AND THEORY 239 



tendency toward variation; the more complex, 

 the greater the opportunity for individual 

 differences. 



So, in the simpler subkingdoms, and in the 

 more general divisions down to and includ- 

 ing the order, the lines of division are more 

 readily differentiated, and the work of classi- 

 fication has been fairly free from differences of 

 opinion. 



But as the order breaks up into families, and 

 the family breaks up into genera, and the genus 

 breaks up into species, and the species breaks up 

 into varieties, and variations tend more and more 

 to carry the individual away from its kind, there 

 are to be found dissensions and differences of 

 opinion which could hardly be chronicled in 

 eight full volumes of this size. 



Nor is the divergent opinion surprising. 



It is said that, of an iceberg floating in the sea, 

 but one-eighth is visible to the surface observer, 

 while seven-eighths of the mass is submerged 

 beneath the water line. 



Who, from looking at the one-eighth in view, 

 could be expected to draw an accurate detail 

 picture of the iceberg as a whole? 



The vegetable kingdom which presents itself 

 to our vision to-day has been under close scientific 

 observation, at most, but a few hundred years. 



