74 PEOCEEDINOS OF TlIK 



The great mass of vascular plants, which he derives from the 

 Primofilices (Mr. Arber's name for the early Ferns), belong to the 

 Phyllineic, with true leaves, differentiated from tlialloid branches or 

 system of branches, as already explained. He divides the Phylliuese 

 into four groups : — 



1. The MacrophylIine£e. — Leaves large and dominant in com- 



parison with the stem. Primofilices and Ferns generally ; 

 l'teridos|)erms or Cycadofilices ; Cycaduphyta. 



2. The Microphyllinea}. — Leaves reduced in comparison with 



the dominant stem. Cordaitea:; ; Ginkgoales ; Coniferae. 



3. The Mesophyllineie. — Leaves intermediate, as regards these 



relations, between groups 1 and 2. = Angiosperms. The 

 latest developed of all the groups and the most higiily 

 adapted to special conditions, sometimes simulating Macro- 

 ])livllinea^ {e. r/. Palms), sometimes MicrophvUinese {e. q. 

 Heaths). 



4. The Articulata?. — Allied to the Macrophyllinese, from which 



they became detached at the epoch of their ancestors, the 

 Primofilices. Characterized by verticillate symmetry, pro- 

 gressive reduction of leaves, radiate arrangement of leaflets, 

 and tendency to multiply the planes of cauline symmetry. 

 This includes the Equisetales, mainly, and the >Sphenophylls, 

 wholly, a Palaeozoic group. 



It is at this point that Prof. Lignier's views have perhaps 

 exercised the greatest influence on botanical opinion. A very 

 few years ago it became customary to associate the Articulatcc 

 with the Lycopods, for which fossil evidence seemed to speak, the 

 characters in common being mainly anatomical. Prof. Jeffrey 

 was the strongest advocate of this view , and, as is well known, 

 divided all vascular plants into Lycopsida and Pteropsida ; the 

 former including Lycopods, Equisetales and Sphenophylls, the' 

 latter all other Yasculares. 



This classification was based partly on the microphylly of the 

 Lycopsida, the megaphylly of the Pteropsida. and partly on certain 

 anatomical characters closely connected with the relative dimen- 

 sions of leaf and stem. Other characters also came in, and the 

 position appeai-ed a strong one ; at any rate I was among those 

 who adopted it for a time. I now think, however, that the 

 Equisetales and Sphenophyllales have been shown by Prof. Lignier 

 not to be really microphyllous at all, but to be derived by re- 

 duction from plants with compound leaves of considerable size. 

 The leaves of the Sphenophylls are generally of some complexity 

 and often deeply divided — it is only their xegutents which have a 

 simple character. Arch rocal ami tes — the oldi-st known member of 

 the Equisetales — had compound, forked leaves, while in Pseudo- 

 hornia, a Devonian representative of the Articulata?, the leaves 

 were doubly compouuil, and were originally taken for fern-fronds. 

 It seems clear from all this, and from the detailed arguments of 

 Prof. Lignier, which I cannot now recapitulate, that the Articulata^^ 



