37 



COAL PLANTS. 



COAL PLANTS. 



38 



been instituted for the purpose of demonstrating how it is really to 

 be explained ; for, considering that all geologists are of accord in the 

 opinion that the plants which formed coal were for a period of some 

 duration floating in water, a partial destruction of them might easily 

 have been supposed to be the result. Professor Lindley has proved 

 that plants are capable of enduring suspension in water in very differ- 

 ent degrees, some resisting a long suspension almost without change, 

 others rapidly decomposing and disappearing. One hundred and 

 seventy -seven plants were thrown into a vessel containing fresh water ; 

 among them were species belonging to the natural orders of which 

 the flora of the coal-measures consists, and also to the common 

 orders, which, from their general dispersion over the globe at the 

 present day, it might have been expected should be found there. In 

 two years one hundred and twenty-one species had entirely disap- 

 peared ; and of the fifty-six which still remained, the most perfect 

 specimens were those of Coniferous Plants, Palms, I/ycopodiace(e, and 

 the like ; thus showing in the clearest manner that the meagre cha- 

 rcter of the Coal Flora may be owing to the different capabilities of 

 different plants of resisting destruction in water. The same experi- 

 ment accounts for the want of fructification in fossil ferns ; for it 

 showed that one of the consequences of long immersion in water is 

 a destruction of the fructification of those plants. 



A much more important fact is the presence of certain tropical 

 forms of vegetation, such as tree-ferns, in the coal ; and the quasi- 

 tropical character of other species, as A rawcarm-like Coniftrte. This 

 is the more startling when connected with another fact, that the coal- 

 measures of Newcastle are of the game age as those of Newfoundland, 

 and even of Melville Island, in 75 N. lat 



From this it has been inferred that the northern parts of the world 

 enjoyed in remote ages a climate where frost and snow, and the incle- 

 ment seasons of arctic regions were unknown ; that they were at least 

 aa hot as equinoctial countries now are ; anil that the inhospitable 

 hyperborean plains of Melville Island at one time displayed the noble 

 scene of a luxuriant and stately vegetation. Palms, it has been said, 

 were there, and they are the especial and princely denizens of the 

 tropics ; tree-ferns occur, and they now only exist in the primeval 

 forests of the torrid zone, haunting their deepest recesses, breathing 

 a damp and equable atmosphere, and living, like vegetable eremites, 

 withovit even a parasite to fix itself upon their trunks and keep them 

 company. Stiymaritt, Myi/larite, and even Catamite* have been 

 enlisted in the cause of this theory, notwithstanding that no one can 

 gay what they may have been. And in confirmation of all this, the 

 preponderance of ferns has been appealed to as having its parallel 

 nowhere except in the hottest and dampest islands of Polynesia. 



In opposition to this view it has been asserted that the presence of 

 these tropical forms of vegetation in northern latitudes is no proof of 

 what the climate in which they were deposited formerly was, because 

 they may have been drifted to their present situations by currents. 

 The perfect state of many of the remain* offers however great diffi- 

 riilti.-i in the way of this supposition; for although they are very 

 iiiiic'h broken, yet the angles of most fossil plants are by no means 

 water-worn, and in Siyillaria, &c. are as sharp as they ever were. 

 Nor is the state of those tropical stems and fruits, which in modern 

 times reach the coasts of Ireland and Norway, at all like that of the 

 buried plants of the coal-measures. 



Another difficulty in the way of admitting a high temperature in 

 northern regions in former days is suggested by considering the dura- 

 1 the days. Without a diurnal change of light and darkness 

 cannot exist ; absence of light blanches them, by the accumu- 

 lation of undecomposed carbonic acid ; absence of darkness destroys 

 or dwarfs and deforms them, by the incessant decomposition of their 

 carbonic acid. Now, however this may be reconciled with a country 

 like England, in which the winter days are of moderate length, it is 

 lew reconcilable with the northern parts of North America, and not 

 at all with Melville Island, in which there are 94 days when the sun 

 is never above the horizon, and 104 days that he never sets. With 

 regard to the transportation of the coal, the absence of indications of 

 washing, and the frequent occurrence of upright stems, seem to lead 

 to the conclusion that in most instances the plants which formed coal 

 have grown at the most within a few hundred miles of th"e places 

 where they are now deposited, and probably in their very vicinity. 

 From this statement we must at present except the coal of Melville 

 Island ; for although the vegetable impressions in the English coal- 

 meaaurea are by no means water-worn, yet those in the British 

 Museum from Melville Island are so rubbed and damaged that there 

 is no doubt they have travelled long distances before they were 

 t,r.t\. 



'I in' opinion that the plants of the coal-meneurea afford evidence 



he climate where they grew must have been tropical, has been 



founded upon three classes ot facts, each of which rer|nires separate 



examination ; the one, the excessive development of certain forms of 



vegetati'-n ; :m-.ther, the presence of tho remains of palms and tree- 



which are usually considered incapable of existing unlens in a 



il atmosphere; the third, the excessive disproportion of ferns 



t'> nthcr [>lnt. 



With regard to the first argument it may be answered, that we 



know too littlo r>f Hi" real nature of the SigiUnriir, Lepidodcndra, 



nd other plant, to Wrm a correct opinion. It is almost 



certain that all these plants are in reality destitute of living analogies ; 

 and therefore as we do not know what they were, we have uo means of 

 judging what kind of climate they required. Supposing that some of 

 the Lepidodendra were closely allied to the modern genus A raucaria, as 

 is highly probable, yet that fact does not afford any proof of a tropical 

 climate; for Araucaria Dombeyi now inhabits the cold mountains of 

 southern Chili, and is at this day uninjured in the severest of our 

 English winters : while Cunniitghamia Sinentis, and species of Callilris 

 or Dacrydium, with which other remains of Lepidodcndra may be 

 compared, although not European, are by no means of tropical habits, 

 but are found on the mountains of New Zealand aiid Van Diemen's 

 Land, where they are exposed to a far from temperate climate. 

 Moreover, Salieburia adiantifolia, which would certainly be considered 

 a tropical form of Coniferrs, if found in an extinct state only, is one of 

 the hardiest of trees, and a native of the rigorous climate of Japan. 

 But even supposing Sigillaria could be found to have beeu succuleut 

 plants, allied to Cactacece or uphorbiacece, as some think, still no real 

 evidence of their having required a tropical climate for their develop- 

 ment would be afforded by them, because there is nothing in the mere 

 organisation of succulent plants which unfits them for cold climates. 

 A capability of enduring cold is something immaterial and independ- 

 ent of organisation, about which nothing can be judged a priori ; for 

 turnips, cabbages, Jerusalem artichokes, house-leek, and many other 

 hardy plants are in parts as succulent as Cactacece. All arguments 

 therefore to prove that the north of Europe was formerly tropical, 

 deduced from the presence of such plants as those now mentioned, 

 are inadmissible. 



Nor is the argument derived from the presence of palms and tree- 

 ferns of much greater force. In the first place, we have seen that 

 there is really no grounds for believing that palms existed ; and as for 

 tree-ferns, we have them in New Zealand, and especially on the south 

 side of Van Diemen's Land, where the mean temperature probably 

 does not exceed 54 Fahrenheit. So that, all things considered, it 

 is by no means safe to take the remains of these plants as good evi- 

 dence of a tropical climate, or of a climate materially unlike that 

 which we now experience. 



The only remaining argument to be considered is that derived from 

 the great preponderance of ferns in the Coal Flora. It is said by 

 Adolphe Brongniart, that as it is only in damp tropical regions that we 

 now find ferns equal in the number of thejr species to all the species 

 of other plants, and as this same proportion is found in the Coal 

 Flora, that therefore the climate under which the Coal Flora was 

 produced must have been damp and tropical. But as, by the experi- 

 ment already mentioned, it was shown that when a given number of 

 plants of entirely different habits are plunged into the same vessel of 

 water, by far the greater part is decomposed before ferns begin to 

 be affected, it is obvious that no estimate of what the proportion of 

 ferns to other plants really was, can now be formed ; and consequently 

 this argument also falls to the ground. 



From these facts it appears then that we may safely adopt the fol- 

 lowing conclusions : 



1. That coal is of vegetable origin. 



2. That at the period of its deposit, the earth was covered with a 

 rich vegetation, of which only a small portion has been preserved ; 

 and that of this portion all the species and several of the races are 

 totally unknown at the present day. 



3. That the climate may possibly have been something milder than 

 it now is, but that there is no evidence in the vegetable kingdom to 

 show that it was materially different from that of the present day. 



The following is a list of the species of plants that have been found 

 in the coal-measures of Great Britain, as given by Professor Tennant 

 in his ' Stratigraphical List of British Fossils.' Very few species indeed 

 appear to have been found in other parts of the world that are not 

 found in Great Britain : 



A letkoptherii Cittii, Goppi 



A. keterophylla, Gopp. 



A. Lindleyana, Presl. 



A. limrliiiidii, Sternb. 



A. Mantelli, Gopp. 



A. nerroa, Gopp. 



A. Sauverii, Gopp. 



A. Kerra, Gopp. 



A. Serlii, Gopp. 



A . urophylla, Gopp*. 



A. vulgatior, Sternb. 



Anabathra pulchei'rima, Lindley. 



Annuhi'i'i" f< rtil'm, Sternb, 



A. longifolia, Broug. 



Antkolil/ies anom.alw, Morris. 



A. Pitcairnia, Lindley. 



Aphlebia adnatcenn, Presl. 



Artitia approximata, Brong. 



A . distant, Brong. 



A . traiwverga, Presl. 



Aspidiaria Anfjlica, Presl. 



A. confuens, Precl. 



A, cristata, Presl. 



A, quadrangular^, Presl. 

 A. urtdula/a, Presl. 

 Aiteraphijllitei comosus, Lindley. 

 A . folioius, Liudley. 

 A. galimdes, Lindley. 

 A.jubatus, Lindley. 



A. rigidui, Lindley. 

 Bechera charctformii, Sternb. 



B. grandit, Sternb. 



Borrtia equisetiformis, Sternb. 

 Bt'uckinannia grandis, Liudley. 

 B. longifolia, Sternb. 

 B, ritjida, Sternb, 

 B. tenuifolla, Sternb. 



B. tuberculata, Sternb. 

 Calamites approsimatut, Brong. 



C. cannffformis, Schlot. 

 C. Cietii, Brong. 



C. decoratus, Brong. 

 C. dubius, Brong. 

 C. intfffnatis, Brong. 

 C. Lindle.yi, Sternb. 

 C. tiodoatis Schlot. 



