532 



SCIENCE. 



[Vol. II., No. 87- 



separated into two schools on the subject. Dawson, 

 Eenault, Grand-Eury, and Saporta adhere to the 

 Brongniartian idea; whilst the British and German 

 paleontologists have always adopted the opposite 

 view, i-ejecting the idea that any of these plants 

 were other than cryptogams. 



A fundamental feature of the entire group is In 

 the fact that their foliar appendages, however mor- 

 phologically and physiologically modified, are arranged 

 in nodal verticils. This appears to be the only char- 

 acteristic which the plants possess in common. 



Calamites and Calamodendron. — In his ' Prodrome ' 

 (182S), and in his later ' V^g^taux fossiles,' Bron- 

 gniart adopted the former of these generic names as 

 previously employed by Suckow, Sclilotheira, Stern- 

 berg, and Artis. It was only iu his ' Tableau des genres 

 de vegiStaux fossiles' (Dictionnaire universel d'his- 

 toire naturelle, 1849) that he divided the genus, intro- 

 ducing the second name to represent what he believed 

 to be the gymnospermous division of the group. A 

 long series of investigations, extending over many 

 years, has convinced me that no such gymnospermous 

 type exists.! The same conclusion has more recently 

 been arrived at by Vom c. M. D. Stur," after studying 

 many continental examples in which structure is 

 preserved. What I regard as an error appeal's to 

 have had an intelligible origin, — the fertile source of 

 similar errors in other groups. 



Nearly all the Calamitean fossils found in shales 

 and sandstones consist of an inorganic, superficially 

 fluted substance, coated over with a thin film of 

 structureless coal (see ' Histoire des v^ge'taux fossiles,' 

 vol. i. pi. 22) ; the latter being exactly moulded upon 

 and followbvj the outlines of the inorganic fluted cast 

 that underlies it. Brongniart, and those who adopt 

 his views, believe that the external surface of this 

 coal-film exactly represents the corresponding exter- 

 nal surface of the original plant: hence the conclu- 

 sion was arrived at, that the plant had a very large 

 central fistular cavity, surrounded by a very thin layer 

 of cellular and vascular tissues, as in some living 

 equisetums. On the other hand, Brongniart also 

 obtained some specimens of what he primarily be- 

 lieved to be Calamites, in which the central pith was 

 surrounded by a thick layer of woody tissue arranged 

 in radiating laminated wedges, separated by medul- 

 lary rays. The exogenous structure of this woody 

 zone was too obvious to escape his practised eye. 

 But, not supposing it possible that any cryptogam 

 could iDossess a cambium-layer and an exogenous 

 mode of development, Brongniart came to the con- 

 clusion that the thin-walled specimens found in the 

 shales and sandstones were true Equisetaceae, those 

 with the thick, woody cylinders being mere ex- 

 ogens of another type. His conclusion that they 

 were gymnosperms was a purely hypothetical one, 

 since justified by no one feature of their organiza- 

 tion. 



My researches, based upon a vast number of speci- 

 mens of all sizes, from minute twigs little more than 

 the thirtieth of an incli in diameter to thick stems 

 ' Memoirs i., ix., .incl xii. 

 ■■= Ziir niorpholoffie der ciiiamarien. 



at least thirteen inches across, led me to the conclu- 

 sion that we have but one type of calamite, and that 

 the differences which misled Brongniart are merely 

 due to variations in the mode of their preservation.' 

 It became clear to me that the outer surface of the 

 coaly film in the specimens preserved in the shales 

 and sandstones did not represent the outer surface 

 of the living plant, but was only a fractional remnant 

 of the carbon of that plant, which had undeigone a 

 complete metamorphosis. The greater part of what 

 originally existed had disappeared, probably in a gas- 

 eous state; and the little that remained, displaying no 

 organic structure, had been moulded upon the under- 

 lying inorganic cast of the medullary cavity. This 

 cast is always fluted longitudinally, and constructed 

 transversely at intervals of varying lengths. Both 

 these features were due to impressions made by the 

 organism upon the inorganic sand or mud filling the 

 medullary cavity whilst it was in a plastic state, and 

 which subsequently became more or less hardened;: 

 the longitudinal grooves being caused by the pressure 

 of the inner angles of the numerous longitudinally 

 vascular wedges, and the transverse ones partly by 

 the remains of a cellular nodal diaphragm which 

 crossed the fistular medullary cavity, and partly by 

 a "centripetal encroachment of the vascular zone at 

 each of the same points.^ 



My cabinets contain an enormous number of sec- 

 tions of these plants, in which the minutest details of 

 their organization are exquisitely preserved. These 

 specimens, as already observed, show their structure 

 in every stage of their growth, — from the minutest 

 twigs, to stems more than a foot in diameter. Yet 

 these various examples are all, without a solitary ex- 

 ception, constructed upon one common plan. That 

 plan is an extremely complicated one, — far too com- 

 plex to make it in the slightest degree probable that 

 it could co-exist in two such very different orders of 

 plants as the Equisetaceae and the Gymnospermae." 

 Yet, though very complex, it is, even in many of its- 

 minuter details, unmistakably the plan upon which 

 the living equisetums are constructed. The resem- 

 blances are too clear, as well as too remarkable, in my 

 mind, to leave room for any doubt on this point. 

 The great differences are only such as necessarily 

 resulted from the gradual attainment of tlie arbores- 

 cent form so unlike the lowly herbaceous one of their 

 living representatives. On the other hand, no living 

 gymnosperni possesses an organization that in any 

 solitary feature resembles that of the so-called Cala- 

 modeudra. The two have absolutely nothing in 

 common: hence the conclusion that these Calamo- 

 dendra were gymnospermous plants is as arbitrary an 

 assumption as could possibly be forced upon science, 

 — an assumption that no arguments derived from the 

 merely external asjjects of structureless specimens 

 could ever induce me to accept. 



These Calamites exhibit a remarkable morphologi- 

 cal characteristic, which presents itself to us here 

 for the first time, but which we shall find recurs in 

 other paleozoic forms. Some of our French botani- 



' Memoirs i. anil ix. 



- See Itemoir i., pi. xxiv., tig, 10: anil pi. xxvi.. Hi!. 24. 



