350 PAST succession: the ceneosere. 



then as now, and it resulted in seres which were both primary and secondary 

 in nature and which fell into series or coseres. Glacial and interglacial epochs 

 produced the shifting of zones, and a resulting sequence of climaxes, or a clisere, 

 in the Permian as in the more recent Pleistocene. Climax zones or areas 

 coincided with climatic zones or areas, and their arrangement foreshadowed 

 the movement of the clisere as it does at present. 



The formation showed both climax and developmental units, and the latter 

 were often likewise zoned in the order of the developmental stages. This 

 correspondence of structural zones and serai stages or associes during the Ceno- 

 phytic era must have been essentially what we see to-day. The differences of 

 the flora and the absence of certaia Ufe-forms, notably the grasses and sedges, 

 produced some striking differences of detaU in the Paleophytic and Meso- 

 phytic eras. However, the general principle that zonation is an epitome of 

 succession must have been fundamental at all times. Throughout the Ceno- 

 phytic the differentiation of formational units must have been as great as at 

 present, or even greater if we admit the current conception of the floral com- 

 plexity. The climax stage must have consisted of associations, consociations, 

 societies, and clans. The initial stage would have shown families and colonies, 

 and all the later serai stages or associes would contain consocies, socies, and 

 colonies. The number of units would have been somewhat less during the 

 earlier eras, particularly since there were fewer relict communities from pre- 

 ceding floras, but probably all the units were represented. Aspects were 

 clearly less developed, since the differentiation of seasons could hardly have 

 gone so far. Layers were undoubtedly present, and in life-form, as frequently 

 in species, must have been more or less continuous with the scrub zone lying 

 around the forest. 



The life-forms of the Cenophytic were those of to-day, as is true of a majority 

 of the genera even. It may be assumed that the Eophj^ic possessed only 

 algse, lichens, and other fungi, liverworts, mosses, and perennial herbs. To 

 these the Paleophytic added trees and shrubs. Both the Paleophytic and 

 Mesophytic lacked grasses, sedges, and annual herbs in particular, but the 

 r61e of reeds and rushes must have been well played by Equisetites and Equi- 

 setum. The development of a dominant scrub form, represented by Bennet- 

 titales, must have been a marked feature of the Mesophytic. The competition 

 and dominance of life-forms could have shown little departure from the present 

 processes, and it is equally certain that every reaction now known existed 

 throughout the four vegetation eras. In the Paleophytic, the reaction upon 

 light and the consequent layering must have been less pronounced, owing to 

 the narrow leaves of the dominants. The coal stases of the three eras show 

 that the reactions of swamp vegetation were essentially those of peat-bogs at 

 present. Aggregation, migration, and ecesis went on practically as they do 

 to-day, except for minor differences involved in the dominance of spore-plants 

 during the Eophytic and Paleophytic. 



Finally, the course of succession was always progressive, except in the case 

 of an unfavorable change of climate, such as glaciation, and was controlled by 

 initial and ecesic causes which led to stabilization. Initial causes produced 

 primary and secondary bare areas for invasion in the same manner as at present. 

 The r61e of topographic causes, erosion, deposit, flooding, and draining, must 

 ave been wholly as it is to-day, except that these processes were more active. 



