THE PALEOSERE. 



421 



Dunkard 



Series 



135-165 



Mononga- 



hela 



Series 



168-226 



m 



i 



Cone- 



maugli 



Series 



231-358 



Allegtieny 



Series 



125-382 



Pottsville 

 Series ' 

 131-386 



m 





Fig. 45. — Section 

 of the Coal 

 Measures in 

 Ohio. After 

 Haseltine. 



terids and other fernworts seems at least not improbable. This 

 stage was not essential to the succession in water-bodies, since 

 charads and diatoms, together or alone, were quite able to shal- 

 low ponds and lakes to the point where amphibious plants could 

 ecize. The colonization of swamps by the latter must also 

 have been frequently and readUy effected during the Mississip- 

 pianand Pennsylvanian, when water-levels were so repeatedly 

 changed by oscillations or minor climatic cycles. The reed- 

 swamp associes of to-day was probably constituted by the 

 smaller Calamites, with amphibious ferns and pteridosperms 

 as codominants or subdominants. Associes corresponding to 

 the sedge and scrub stages of to-day were either lacking, or, 

 more probably, were represented by taller species of Calch 

 mites. The form and structure of the latter indicates that 

 they could not have grown in close association with the more 

 lofty Lepidodendrese and Cordaites, since they are entirely 

 without adaptations to shade. As to the final stages, the 

 form of the stems of Sigillaria, Lepidodendron, and Cordaites, 

 as well as their leaf habits, suggests that they were not codomi- 

 nants of the characteristic climax of the Paleophytic. On 

 purely ecological grounds, Cordaites should have constituted 

 the climax, while Lepidodendron and Sigillaria may well 

 have formed the subclimax, but with the latter taking the 

 initiative in the stage. Such a sequence is indicated by their 

 probable reaction upon light especially, but it is wholly hypo- 

 thetical at present. In the consocies or mictia formed by 

 these universal dominants, there doubtless developed layers 

 of tree-ferns and pteridosperms, of Sphenophyllum and filicals, 

 and of Selaginella, Miadesmia, etc. If Glossopteris existed as 

 a climax dominant before the Permian, the early develop- 

 ment of its sere must have been essentially like the above. 

 In the cooler or drier climates characterized by Glossopteris, 

 however, the development of forest was impossible, and the 

 cUmax was reached in a scrub or even an herbaceous stage. 

 The cosere. — Coseres were typical of the Pennsylvanian in 

 particular. The characteristic swamps of the period fur- 

 nished conditions for the development of the hydrosere not 

 imlike those of the swamps and peat-bogs of to-day. Fre- 

 quent changes of level in the swamp destroyed and buried 

 the Uving vegetation and its accumulated remains, forming 

 seams and beds of coal. From the standpoint of succession, 

 it is immaterial whether the changes of the swamps were due 

 to oscillation, to submergence and consequent sedimentation, 

 or to climatic cycles. It seems most probable that all of these 

 destroyed swamp vegetation and produced a new bare area 

 at one time or another. Pure beds or seams of coal apparently 

 represent the continuous growth and accumulation of a 

 climax vegetation. They correspond to a sere, and are to be 

 regarded as stases, though the period of accumulation repre- 



