OCTOBEK 13, 1911] 



SCIENCE 



^11 



has been recently reexplored at the in- 

 stance of Professor Potonie, and he finds 

 it to agree closely with the vegetative pe- 

 culiarities which he considers must have 

 been presented by the vegetation of the 

 coal-measure forest. A typical "Sump- 

 flachmoor, ' ' this highly interesting tropical 

 swamp has produced a deposit of peat 

 amounting in some places to thirty feet in 

 thickness. The peat itself consists mainly 

 of the remains of the Angiospermic vegeta- 

 tion of which the forest is made up, in- 

 cluding pollen-grains and occasional fungal 

 filaments; the preservative power, which 

 has enabled this accumulation of debris to 

 take place, being due to the peaty water 

 which is seen above the roots of the bulk of 

 the vegetation. The latter consists mainly 

 of dicotyledonous trees belonging to vari- 

 ous natural orders, and they mostly show 

 such special adaptations as breathing roots 

 (pneumatophores) and often buttress roots. 

 With the exception of a tree-fern, Pterido- 

 phyta. Liverworts and Mosses, and, indeed, 

 all herbaceous vegetation, are poorly repre- 

 sented in this swamp, though high up in 

 the branches of the trees there are a fair 

 number of epiphytes, and at the edge of the 

 swamp-forest lianes, belonging particularly 

 to the palms, play an important part in the 

 vegetation. The water, partly on account 

 of its peaty nature, partly owing to the 

 intense shade, is almost devoid of algse, and 

 none of these organisms were found in the 

 peat itself. The interesting account given 

 by Potonie of this tropical peat-formation 

 is very suggestive when certain features, 

 as, for example, the absence or relative 

 paucity of certain of the lower groups of 

 plants, such as alga and Bryophyta, in the 

 peat, are compared with the plant-remains 

 in some of our coal-seams. Replacing the 

 now dominant Angiosperms by their Pteri- 

 dophytie representatives in paleozoic times, 



we have a very close parallel in the two 

 formations. 



Another interesting question arises when 

 we consider the great variety of types of 

 vegetation met with among the plant-re- 

 mains of the coal-seams. For in addition 

 to the limnophilous Calamites and Lepido- 

 dendracece mentioned above, the coal-balls 

 abound with the remains of representatives 

 of the Filicales, the PteridospermEe and the 

 Cordaitacete. Were these also members of 

 this swamp vegetation, or have their re- 

 mains been carried by wind or water from 

 surrounding areas? With regard to some 

 plant-remains, namely, those found exclu- 

 sively in the roof nodules, the latter was 

 undoubtedly the case; for we have ample 

 evidence, both in their preservation and 

 their mode of occurrence, that they have 

 drifted into the region of the coal-measure 

 swamp after its submergence below the sea. 

 This would apply to such plants as Tu- 

 bicaulis Sutcliffii (Stopes), Sutcliffa in- 

 signis (Scott), Cycadoxylon robustum and 

 Poroxylon Sutcliffii and other forms, the 

 remains of which have so far not been 

 observed in the coal-seam itself. These 

 plants represent a vegetation of non- 

 aquatic type, and may be taken to have 

 grown on the land areas surrounding the 

 paleozoic swamps. But, on the other hand, 

 we have remains of many non-aquatic 

 plants in the coal-seam itself, closely asso- 

 ciated with fragments of typical marsh- 

 plants. How can their juxtaposition be 

 explained ? 



The advance of our knowledge of ecol- 

 ogy points, I think, to a solution of this 

 difficulty. No feature of this fascinating 

 study, which has of late gained so promi- 

 nent a place in botanical investigation, is 

 more interesting than to trace out the suc- 

 cession of plant associations within the 

 same area, noting the ever-changing condi- 

 tions which the development of each as- 



