OCTOUKK 19, 188;!.] 



SCIENCE. 



537 



lion was preserved. Dawson, Newberry, and Ias- 

 quereux have also shown that many species of similar 

 seeds, though with no traces of internal structure, 

 occur in the coal-measures of North America. 



EiiMally important was the further discovery by M. 

 Graud-Eury, that the Antholithes, with their cardi- 

 ocarpoid seeds, were but one form of the monocli- 

 Dous catkin-like inflorescences of the Noeggerathiae, 

 now better known by Unger's name of Cordaites. 

 These investigations suggest some important con- 

 clusions. 1°. The vast number and variety of these 

 cycadean seeds, as well as the enormous size of some 

 of them, are remarkable, showing the existence of an 

 abundant and important carboniferous vegetation, 

 of most of which no trace has yet been discovered 

 other than those isolated seeds. 2°. Most of the 

 seeds exiiibit the morphological peculiarity of having 

 a large cavity (the 'cavite poUinique' of Brongniart) 

 between the upper end of the nucelle and its invest- 

 ing episperm, and inunediately below the micropile 

 of the seed. That this cavity was destined to have 

 the pollen-grains drawn into it, and be thus brought 

 into direct connection with the apex of the nucelle, is 

 shown by the various examples in which such grains 

 are still found in that cavity.' 3°. M. Grand-Eury 

 has shown that some of his forms of Cordaites pos- 

 sessed the discoid or Sternbergian pith which I had 

 previously found in Dadoxylon. And, lastly, these 

 Cordaites prove that a diclinous form of vegetation 

 existed at this early period in the history of the flow- 

 ering plants, but whether in a monoecious or a dioe- 

 cious form we have as yet no means of determining. 

 Their reproductive structures differ widely from the 

 true cones borne by most cycads at the present day. 



Conifers. — It has long been remarked that few real 

 cones of conifers have hitherto been found in the 

 carboniferous rocks, and I doubt it any such have 

 yet been met with. Large (juantities of the woody 

 stems now known as Dadoxylons have been found, 

 both in Europe and America. These stems present 

 a true coniferous structure, both in the pith, medul- 

 lary, sheath-wood, and bark.- The wood presents 

 one very peculiar feature: its foliar bundles, though 

 in most other respects exactly like those of ordinary 

 conifers, are given off, not singly, but in pair.s.'' I 

 have only found this arrangement of double foliar 

 bundles in the Chinese giiigko (Salisburia adianti- 

 folia).* This fact is not unimportant when connected 

 with another one. Sir Joseph Hooker long ago ex- 

 pressed his opinion that the well-known Trigono- 

 carpons' of the coal-measures were the seeds of a 

 conifer allied to this Salisburia. The abundance 

 of the fragments of Dadoxylon, combined with the 

 readiness with which cones and seeds are preserved in 

 a fossil state, makes it probable that the fruits belong- 

 ing to these woody stems would be so preserved; but 

 of cones we find no trace, and, as we discover no 



' ^fctnoir viii., pi. il., Ilgs. 70 and 72. Brongniart, Kcchcrcbcs 

 >ur ICK griilncs fosailcs •IlicinC'eH, pi. xvi., ligs. 1, 2; pi. xx., lig. 2. 



' Dr. DawaoQ fiudu tile iliacoid pilh in one of the living Cana- 

 dian conifers. 



' .Memoir vlll., pi. Ivlll., lig. 4«; and pi. ix., tiga. 44-46. 



« M.inulr xii., pi. xxxlll., flgs. 2S, 2J. 



■ Moninlr viil , tig». 94-11.'). 



Other pl.int in the carboniferous strata to which the 

 Trigonocarpons could with any probability have be- 

 longed, these facts afford grounds for associating 

 them with the Dadoxylons. These combined reasons 

 — viz., the structure of the stems with their character- 

 istic foliar bundles, and the gingko-like character of 

 the seeds — suggest the probability that these Dadoxy- 

 lons, the earliest of known conifers, belonged to the 

 Taxineae, the lowest of these coniferous types, and 

 of which the living Salisburia may perhaps be re- 

 garded as the least advanced form. 



Thus far our attention has been directed only to 

 plants whose affinities have been ascertained with 

 such a degree of probability as to make them avail- 

 able witnesses, so far as they go, when the question 

 of vegetable evolution is aub judice. But there re- 

 main others, and probably equally important ones, 

 respecting which we have yet much to learn. In 

 most cases we have only met with detached portions 

 of these plants, such as stems or reproductive struc- 

 tures, which we are unable to connect with their other 

 organs. The minute tissues of these plants are pre- 

 served in an exquisite degree of perfection: hence we 

 are able to affirm, that, whatever they may be, they 

 differ widely from every type that we are acquainted 

 with amongst living ones. The exogenous stems or 

 branches from Oldham and Halifax which I described 

 under the name of Aslromyelon,' and of which a much 

 fuller description will be found in my forthcoming 

 Memoir xii., belong to a plant of this description. 

 The remarkable conformation of its bark obviously 

 indicates a plant of more or less aquatic habits, since 

 it closely resembles those of Myriophyllum, Marsilea, 

 and a number of other aquatic plants belonging to va/- 

 rious classes. But its general features suggest nearer 

 affinities to the latter genus than to any other. An- 

 other very characteristic stem is the Heterangium 

 Grievii,'' only found in any quantity at Burntisland, 

 but of which we have recently obtained one or two 

 small specimens at Halifax. This plant displays an 

 abundant supply of primary, isolated, vascular bun- 

 dles, surrounded by a very feeble development of 

 secondary vascular tissue. Still more remarkable is 

 the Lyginodendron Olilhamium,^ a stem not uncom- 

 mon at Oldham, and not uiifrequently found at 

 Halifax. Unlike the Heleraiigium, its primary vas- 

 cular elements are feeble, but its tendency to develop 

 secondary zylem is very characteristic of the plant. 

 An equally peculiar feature is seen in the outermost 

 layer of its cellular bark, which is penetrated by in- 

 numerable longitudinal lamin.ie of proscnchymatous 

 tissue, which is arranged in precisely the same way 

 as is the hard bast in the lime and similar trees, 

 atfording another example of the introduction into 

 the outer bark of the ' appareil de soutieit.' As might 

 have been anticipated from this .iddilion to the bark, 

 this plant attained arborescent dimensions, very large 



' Memoir fx., In which I only described decorticated npecl. 

 mcn». Messrs. Cash und Ilclk described a specimen in which 

 the peculiar bark was preserved under the nnrae of Aalrcimyeion 

 Wiiliamsonls. See Proceedings of the Yorkshire polytechnic so- 

 ciety, vol. vll. part iv., 1881. 



■■ Memc.ir ill. /lii'i. 



