530 



SCIENCE. 



[Vol. II., No. 37. 



conclusions. But the common state in which our 

 fossil plants are preserved presents a source of error 

 that is positive as well as negative. Most of those 

 from our coal-measures consist of inorganic shale, 

 sandstone, or ironstone, invested by a very thin layer 

 of structureless coal. The surface of the inorganic 

 substance is moulded into some special form, depend- 

 ent upon structural peculiarities of the living plants; 

 which structures were sometimes external, some- 

 times internal, and sometimes intermediate ones. 

 Upon this inorganic cast we find the thin film of 

 structureless coal, which, though of organic origin, 

 is practically as inorganic as the clay or sandstone 

 which it invests ; but its surface displays specific 

 sculpturings, which are apt to he regarded as always 

 representing the outermost surface of the plant when 

 living, whereas this is not always the case. That the 

 coaly film is a relic of the carbonaceous substance of 

 the living plant is unquestionable ; but the thinnest 

 of these films are often the sole remaining represen- 

 tatives of structures that must originally have been 

 many inches, and in some instances even many feet, 

 in thickness. In such cases most of the organic ma- 

 terial has been dissipated, and what little remains 

 has often been consolidated in such a way that it is 

 merely moulded upon the sculptured inorganic sub- 

 stance which it covers, and hence affords no infor- 

 mation respecting the exterior of the fossil when a 

 living organism. It is, in my opinion, from speci- 

 mens like these, that the smooth bark of the Calamite 

 has been credited with a fluted surface, and the 

 Trigonocarpons with a merely triangular exterior and 

 a misleading name, as it long caused the inorganic 

 casts known as Sternbergiae to he deemed a strange 

 form of plant, that had no representative amongst 

 living types. In other cases the outermost surface 

 of the bark is brought into close contact with the 

 surface of the vascular cylinder. I have a Stigmaria 

 in which the bases of the rootlets appear to be planted 

 directly upon that cylinder, the whole of the thick 

 intermediate bark having disappeared. In other ex- 

 amples, that vascular zone has also gone. Thus the 

 innermost and outermost surfaces of a cylinder, origi- 

 nally many inches apart, are, through the disappear- 

 ance of the intermediate structures, brought into 

 close approximation. In such cases, leaves and other 

 external appendages appear to spring directly from 

 what is merely an inorganic cast of the interior of 

 the pith. I believe that many of onr Calamites are 

 in this condition. Such examples have suggested 

 the erroneous idea that the characteristic longitudi- 

 nal fiutings belong to the exterior of the bark. 



Fungi. — Entering upon a more detailed review of 

 our knowledge of the carboniferous plants, and com- 

 mencing at the bottom of the scale, we come to the 

 lowly group of the fungi, which are unquestionably 

 represented by the Peronosporites antiquariusi of 

 Worthington Smith. There seems little reason for 

 doubting that this is one of the phycomycetous fungi, 

 possibly somewhat allied to the Saprolegnieae; but 

 since we have, as yet, no evidence respecting its fructi- 

 fication, these closer relationships must for the present 

 1 Memoir xi. p. 299. 



remain undetermined. So far as I know, this is the 

 only fungus satisfactorily proved to exist in the car- 

 boniferous rocks, unless the Escipulites Neesii of 

 Goeppert, and one or two allied forms, belong to the 

 fungoid group. The Polyporites Bowmanni is un- 

 questionably a scale of a holoptycliian fish. 



Algae. — Numerous objects siipposed to belong to 

 this family have been discovered in much older rocks 

 than carboniferous ones. The subject is a thorny 

 one. That marine xilants of some kind must have 

 existed simultaneously with the molluscous and other 

 plant-eating animals of paleozoic times, is obviously 

 indisputable; but what those plants were is another 

 question. The widest differences of opinion exist 

 in reference to many of them. A considerable num- 

 ber of those recognized by Schimper, Saporta, and 

 other paleobotanists, are declared by Nathorst to be 

 merely inorganic tracks of marine animals; and, in 

 the case of many of these, I have little doubt that 

 the Swedish geologist is right. Others have been 

 shown to be imperfectly preserved fragments of 

 plants of much higher organization than algae, 

 branches of conifers even being included amongst 

 them. I have, as yet, seen none of carboniferous age 

 that could be Indisputably identified with the family 

 of algae, though there are many that look like and 

 may probably be such. The microscope alone can 

 settle this question, though even this instrument 

 fails to secure unity of opinion In the case of Daw- 

 son's Prototaxites ; and no other of the supposed sea- 

 weeds hitherto discovered have been sufficiently well 

 preserved to bear the microscopic test: hence I think 

 that their existence in carboniferous rocks can only 

 he regarded as an uuproven probability. Mere super- 

 ficial resemblances do not satisfy the severe demands 

 of modem science, and probabilities are an insuffi- 

 cient foundation upon which to build evolutionary 

 theories. 



Seeing what extremely delicate cell-structures are 

 preserved in the carboniferous beds, it cannot appear 

 other than strange that the few imperfect fungoid 

 relics just referred to constitute the only terrestrial 

 cellular cryptogams that have been discovered in the 

 carboniferous strata. The Darwinian doctrine would 

 suggest that these lower forms of plant-life ought to 

 have abounded in that primeval age; and that they 

 were capable of being preserved is proved by the 

 numerous specimens met with in tertiary deposits. 

 Why we do not find such in the paleozoic beds is 

 still an unsolved problem. 



Vascular cryptogams. — The vascular cryptogams, 

 next to he considered, burst upon us almost sudden- 

 ly, and in rich profusion, during the Devonian age. 

 They are equally silent in the Devonian and carbonif- 

 erous strata as to their ancestral descent. 



Ferns. — The older taxonomic literature of paleo- 

 zoic fern-life is, with few exceptions, of little scien- 

 tific value. Hooker and others have uttered in vain 

 wise protests against the system that has been pur- 

 sued. Small fragments have had generic and specific 

 names assigned to them, with supreme indifference 

 to the study of morphological variability amongst 

 living types. The undifferentiated tip of a terminal 



