110 ELEMENTS OF S HCTURAL BOTANY. 



first of all into comprehensive groups, on the ground of 

 some characteristic possessed by every member of each 

 group. Just as, in Latin, every noun whose genitive 

 case is found to end in ce, is classed with nouns of the 

 first declension, so in Botany, every jDlaut presenting 

 certain peculiarities will be placed in a group along 

 with all the other plaBts presenting the same peculiar- 

 ities. 



178. Some hints have already been given you as to 

 the kind of resemblances upon which classification is 

 based. For instance, an immense number of plants 

 are found to produce seeds with a dicotyledonous 

 embryo, while an immense number of others have 

 monocotyledonous embryos. This distinction, there- 

 fore, is so pronounced, that it forms the basis of a divis- 

 ion into two very large groups. Again, a very large 

 number of dicotyledonous plants have their corollas in 

 separate petals ; many others have them united, whilst 

 others again have no petals at all. Here, then, is an 

 opjiortunity to subdivide the Dicotyledons into poly- 

 petalous, gamopetalous, and apetalous groups. And 

 so we go on, always on the plan that the more widely 

 spread a peculiarity is found to be, the more compre- 

 hensive must be the group based on that peculiarity ; 

 and so it happens, that the smallest groups of all come 

 to depend upon distinctions which are, in many cases, 

 by no means evident, and upon which botanists often 

 find themselves unable to agree. 



179. As our divisions and subdivisions will neces- 

 sarily be somewhat numerous, we shall have to devise 

 a special name for each kind of groui), in order to avoid 

 confusion of ideas. We shall, then, to begin with, 

 d;aw a broad line of "istinction between those plants 



