THE PALEOPHYTIC ERA. 419 



Life-forms and dominants.— Though the record is scanty, the existence of 

 freshwater algae and fungi during the PaJeophytic seems to be beyond doubt. 

 Lichens are unknown, but it is probable that they were in existence, since both 

 components, the alga and the fungus, were available. The record of bryo- 

 phytes is meager and doubtful, although the genera Marchardites and Muscites 

 indicate the existence of both liverworts and mosses. The herb-form is rep- 

 resented by Sphenophyllum, Pseudobarnia, Selaginellites, Botryopteris, Mia- 

 desmia, etc., and the reed-form perhaps by some of the Calamites. The shrub- 

 form is probably represented by Psaronius, Lyginodendron, Neuropteris, 

 Alethopteris, some species of Calamites, Sigillaria, etc., and the trees by Lepi- 

 dodendron, Sigillaria, Calamites, Cordaites, Cardiocarpus, etc. 



As to the serai dominants of the Paleophytic, it is practically certain that 

 algse, charads, lichens, liverworts, and mosses were in existence, and played 

 essentially their present r61e. Of the floating form there is no evidence, but 

 the reed-form must have been well represented by the small species of Cala- 

 mites in particular. As indicated above, the herbaceous and shrubby stages 

 of the sere must have been well developed, while the tree type was not only 

 well represented, but must have given character to a climax formation in 

 which layers of herbs and shrubs were a marked feature. From the standpoint 

 of life-forms and dominants, then, there was little to distinguish the general 

 course of the prisere in the Paleophytic era from that of the present flora, 

 notwithstanding the striking difference in floristic and physiognomy. 



Structure of the vegetation. — ^The presence of so many arboreal types as 

 Calamites, Lepidodendrese, Cordaites, and Ginkgo, and of arborescent ones, such 

 as Psaronius, Neuropteris, and possible cycadeans, indicates a considerable 

 differentiation of vegetation during the Paleophytic. This is supported by the 

 appearance of the Glossopteris flora in the' southern hemisphere as early as the 

 Mississippian period. It also gains further support from the ecological differ- 

 ences of the woody types, as represented by the Calamites-Lepidodendreae 

 form on the one hand, Cordaites and Ginkgo on another, and the pteridophytic 

 form of Psaronius, Neuropteris, etc. Taken in conjunction with the basic law 

 of succession that life-forms mark the concomitant development of the habitat 

 and formation stage by stage, and that this development is reflected in the 

 structure of the vegetation, it seems highly probable that there was some 

 climax and hence climatic differentiation throughout the era. This would not 

 only have been a natural if not inevitable consequence of Silurian-Devonian 

 deformation, but it is also strongly indicated by the appearance of the Glos- 

 sopteris flora with its cold-arid impress during the Carboniferous periods. 

 Perhaps an even stronger argument for a differentiation of climate and vegeta- 

 tion is the fact that the gymnosperms, Cordaites, Ginkgos, and the cycadeans 

 survived the Permo-Triassic crisis, and became dominant at the same time that 

 the Calamites and Lepidodendreae rapidly diminished and disappeared. 

 Ecologically, this can only be interpreted to signify that these types already 

 characterized different climaxes, or potential climaxes during the Paleophytic 

 (Chamberlin and Salisbury, 1906:2:602-603). 



Deformational cycles and climates. — The Paleophytic era was inaugurated 

 by the deformation and glaciation which marked the close of the Proterozoic. 

 The effect of late Proterozoic glaciation is thought to have vanished before 

 the Cambrian, however, and the Lower Cambrian is regarded as exhibiting 



