164 HISTORY OF BOTANY 



found himself constantly in difficulties with the precise 

 limitations of genera, and this led him to undertake his 

 magnum opus, the Genera Planiamm, a work in which, 

 at a later date, he had the invaluable assistance of Sir 

 Joseph Hooker, the distinguished son of the then Director 

 of Kew, Sir W. J. Hooker. 



The fundamental principle on which Bentham and 

 Hooker worked was to start with the genera and smaller 

 associations and allow more general relationships to 

 develop gradually and lead them to higher groupings. 



The scheme ultimately adopted was the following : 



A. Dicotyledons. 



i. Polypetalae. 



Thalamiflorae ; Disciflorae ; Calyciflorae. 

 2 Gamopetalae. 



Inferae ; Superae ; Dicarpeae. 

 3. Monochlamydeae or Incompletae. 



Curvembryae ; Multiovulatae Aquaticae ; 

 Multiovulatae Terrestres ; Micrem- 

 bryae ; Daphnales ; Achlamydosporeae ; 

 Unisexuales ; Ordines Anomali. 



B. Monocotyledons. 



Microspermae ; Epigynae ; Coronarieae ; 

 Calycineae ; Nudiflorae ; Apocarpae ; 

 Glumaceae. 



The special features of this classification are the 

 institution of a group of Disciflorae between De Candolle's 

 Thalamiflorae and Calyciflorae, and a totally new arrange- 

 ment of the Incompletae, plants with flowers possessing 

 a single perianth or none at all, for the recognition of these 

 as reductions from higher " complete " flowers was not 

 as yet at all a familiar conception in the botanical world. 

 We would not dream nowadays of placing plants, other- 

 wise related, in two different categories simply because 

 one was aquatic and the other terrestrial, nor would we 



