80 BOTANY 



described new form. Thus the descriptive floras were 

 the most important part of the literature of the earlier 

 botanists. These and the dried herbaria were, and are, 

 to the botanist what the card index is to the librarian 

 in a huge library. By now most of the species in the 

 inhabited countries are known, but there still remain 

 very many unrecorded species to reward any traveller 

 and careful observer. There are named and described 

 close on a quarter of a million of living species of plants 

 altogether, including the lower and often nearly in- 

 visible forms, and of this vast number about one hundred 

 and thirty thousand belong to the highest group of all 

 the Angiosperms. This fact acquires a further interest 

 when we remember that this group has evolved in such 

 comparatively recent geological times. 



Botany has often been classed with stamp collecting 

 in the older days when the only object of many who 

 went under the name of botanist was to collect and name 

 all the plants of their district, and when the naming of 

 a new species was the ultimate crown of success. It 

 is true that there have been many such in the rank and 

 file of the adherents of the science, but one of the re- 

 markable things about the great systematic botanists 

 of the old school is the insight they obtained into the 

 relations of the innumerable species they described. 

 They not merely labelled and arranged the chaos, they 

 classified the genera into families and cohorts which 

 indicate the scheme of evolution, if not in all its details, 

 at least in its main outlines. 



The living plants may be divided into five main 

 classes according to the complexity and structure of 

 their reproductive organs. This is paralleled in the 

 main by their vegetative structure, so that in general 

 one can recognise a Seaweed, a Moss, a Bracken fern, 



