THE CLASSIFICATION OF PLANTS 2161 



Angiosperms are concerned, except that he places the Monocotyledons 

 last. 



It is impossible here to consider in detail the scheme of classification 

 adopted in each work. It must however be pointed out that the " Genera 

 Plantarum " was never intended to express a complete phylogenetic 

 picture of classification. It was an attempt to extend and elaborate the 

 ideas of De Jussieu and De CandoUe in the light of more recent knowledge. 

 Moreover it was written at a time when the fixity of species was still 

 accepted by many botanists. The Englerian system, on the other hand, did 

 attempt to give a phylogenetic picture and has suffered criticism as a con- 

 sequence. Moreover the " Natiirliche Pflanzenfamilien " was a vast com- 

 pendium of information, collected and written by a number of separate 

 authors whose views on phylogeny were not necessarily identical. 



The most recent treatment of the classification of Flowering Plants on a 

 phylogenetic basis is due to Hutchinson who, in his " Families of 

 Flowering Plants " published in 1926 and 1934, attempted to sift the 

 good in both systems, while at the same time introducing much of his own, 

 derived from a long study of the herbaria at the Royal Botanic Gardens at 

 Kew, and a special knowledge of African plants. 



It is mainly upon the question as to what are to be considered the most 

 primitive orders that the three systems differ. Bentham and Hooker started 

 with the polypetalous families and their first order was the Ranales. From 

 the Polypetalae they proceeded to the Gamopetalae and then finally to the 

 Apetalae, ending up with the Gymnosperms, after which they placed 

 the Monocotyledons. It was largely upon the unfortunate separation of the 

 Apetalae, between the Gamopetalae and the Monocotyledons, that the 

 system was criticized by other authorities. 



The Englerian system amalgamated the Polypetalae and the Apetalae, 

 while the Monocotyledons take precedence over the Dicotyledons. Thus 

 the catkin-bearing trees are considered to be the most primitive Dicotyle- 

 dons and they are followed by the polypetalous Ranalean families. Since 

 the " Pflanzenfamilien " appeared, much evidence has accumulated which 

 points to the primitive nature of the Ranalean families, and though the 

 matter is still questioned by some authorities it seems that the weight of 

 opinion now favours the view that the Polypetalae are the most primitive of 

 Angiosperms and hence that we should consider the Dicotyledons as more 

 primitive than the Monocotyledons. All the evidence about phylogeny, 

 however, indicates that evolution has progressed along divergent paths and 

 in regarding the Polypetalae as the most primitive group we certainly must 

 not deduce that the whole of the Dicotyledons are more primitive than the 

 Monocotyledons, but rather that from a primitive dicotyledonous stock 

 both the higher Dicotyledons and also the Monocotyledons may have 

 developed. 



In this connection it is recognized that, while fossil evidence indicates 

 that the apetalous families can be traced far back into Tertiary^ time and 

 are therefore of early origin, they need not of necessity be considered as 



