GENERAL DESCBIPTION 7 



" In applying these differences to practice, it is 

 necessary to attend to the following rules: 



" The classes are not absolutely distinguished from 

 each other by any one character, but by the combination 

 of their characters. For this reason a plant may have 

 one of the characters of a class to which it nevertheless 

 does not belong, because its other characters are at 

 variance with that class. Thus some species of Kanun- 

 culus have the flowers with their parts in threes ; but 

 they do not on that account belong to Endogens, 

 because their wood is concentric, their leaves netted, 

 and their embryo dicotyledonous. Arum inaculatum 

 has reticulated leaves ; but it is not an Exogen, because 

 its wood is confused, and its embryo monocotyledonous ; 

 its flowers are neither in fours or fives nor threes, all the 

 parts being in a state of peculiarly diminished struc- 

 ture. The genus Potamogeton (a water plant, one of 

 the Naiads) has the flowers in fours ; yet it does not 

 belong to Exogens, because its leaves have parallel 

 veins, and its embryo is monocotyledonous." 



No better \vords could have been written, whether 

 to stimulate the learner to care and thoroughness in 

 research or to rebuke the dogmatism of pedantic 

 system-builders and teach that modesty and liberal 

 allowance of dissent which should characterize the 

 student of Nature and the worshiper of Truth. 



