16 PEOTISTS AND DISEASE 



dangers that they ran, their zeal has cost both them and us 

 their lives. 



Classification or Taxonomy. Any collection of objects 

 can be classified in various ways ; e.g. by size, shape, or 

 colour. Classification is abstract, artificial : as Delage 

 and Herouard have written, " Only individuals exist." Ai] 

 the same we know that without systems of grouping there 

 could be no natural science. On this subject Huxley may 

 be quoted : " Each such assemblage is in fact a ' natural 

 order ' in the sense in which that word is used by botanists, 

 and although the number of these natural orders may be 

 increased by the discovery of new forms, or diminished by 

 the ascertainment of closer bonds of union than are at 

 present known to exist between the orders already dis- 

 criminated, yet the morphological types which they repre- 

 sent will always remain, and therefore the knowledge of 

 their characters, once acquired, will be a permanent 

 possession.'' 



As far as knowledge allows organisms are grouped 

 according to the stock they come from ; their stirpes, as 

 John Ray (1628-1705) called them. Ray was the first to 

 distinguish in flowering plants the two groups, mono- and 

 dicotyledons. 



After the publication of Darwin's " Origin of Species " 

 in 1859, classification became more consciously guided by 

 phylogeny. 



The immense array of living organisms is first broadly 



