The classification of Dicotyledons 



Alfred Gundersen 



Among botanical systems of the past century those of Ben- 

 tham and Hooker and of Engler and Prantl stand out as having 

 received world wide recognition. It is well known that Bessey 

 adopted several points from the Bentham and Hooker system 

 in preference to the Engler system. In 1925 Rendle (4) pre- 

 sented the Engler system with slight modifications, but in 

 part adopted Bentham and Hooker arrangements. The foUow- 

 year Hutchinson (3) in many respects followed the Bentham 

 and Hooker system. The works by Rendle and by Hutchinson 

 may perhaps be considered as modernized forms of the two 

 standard systems ; they were briefly compared in Torreya xxvi : 

 70-75 (1926), where Hutchinson's diagram of dicotyledons is 

 reproduced. 



In 1897 Engler published (1) an early diagrammatic repre- 

 sentation of dicotyledons. In this Parietales and Rhoeadales 

 (Papaverales) are connected, a connection of special significance. 

 More recent diagrams are those of Hallier, Wettstein, Bessey, 

 Clements, and Hutchinson. It may be that in certain features 

 one system is better, in other features another system is super- 

 ior. 



An arrangement more or less intermediate between the 

 Rendle system and the Hutchinson system is here attempted. 

 Arguments against keeping the herbaceous plants as a separate 

 group are strong. In the following outline and diagram the 

 dicotyledons are grouped around eight genera: Magnolia, Ul- 

 mus, Cistus, Dianthus, Geranium, Myrtus, Ligustrum and Rubia. 

 The arrangement, using the words of Rendle, "does not claim 

 to be strictly phylogenetic." 



Magnolia Group (Magnoliflorae) — Perianth parts sepa- 

 rate, stamens often many, carpels usually separate or single. 



Magnoliales Rosales 



Ranales Leitneriales 



The subsequent groups have generally united carpels. 



Ulmus Group (Ulmiflorae) — Usually without petals, 

 often only one seed per ovary, often catkin-bearers. 

 Urticales Fagales 



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