No. 544] BOTANICAL SOCIETY OF AMERICA 217 



than their expression in the present flora can possibly 

 give ; and that this makes a rational phylogeny possible. 



I will address myself in the main, therefore, to phy- 

 logeny, as involving all the taxonomy that is of large im- 

 portance. When paleobotany to-day assembles the great 

 series of paleozoic pteridophytes, the impression is very 

 different from that of a few years ago. It is true that we 

 have always heard of the giant forms of the Paleozoic 

 and their dwarf representatives of to-day. We con- 

 trasted Lepidodendron with Lycopodium, and Calamites 

 with Equisetum, and the total impression was the strik- 

 ing difference in size. 



Now we have learned that these paleozoic Lycopodiales 

 and Eqnisetales were not merely comparatively large, but 

 that they were also comparatively complex. For exam- 

 ple, we have learned that their huge bodies developed 

 secondary wood and had attained heterospory. We be- 

 gin to understand that vascular plants, with the exception 

 of Angiosperms, were as completely differentiated, so 

 far as the great groups are concerned, at the beginning 

 of our records as now; and that the phylogeny in sight is 

 not that of one great group following another, but of all 

 the great groups spraying out into more and more modern 

 expressions. 



Not long ago, our morphology taught that the homo- 

 sporous Lycopodium is the modern representative of the 

 arborescent, paleozoic club mosses, and that the hetero- 

 sporous Selaginella is a modern offshoot. Now we find 

 that the paleozoic forms, with their heterospory, their 

 ligules, and their other structures, link up with Selagi- 

 nella; and we are asking, where are the ancestors of Ly- 

 copodium? Not long ago Isoetes, once suspected of being 

 responsible for the monocotyledons, was fluttering be- 

 tween Filicales and Lycopodiales, and at last had settled 

 down as an anomalous member of the latter group; and 

 now modern paleobotany assures us that its whole struc- 

 ture suggests that it is a much reduced and compacted 

 Lepidodendron. Thus the anomalous Isoetes has a ten- 



