656 



HISTORY OF THE VEGETABLE KINGDOM. 



rows, not leaving clear and well defined 

 soars. 



Ten species in the coal formation. 



One in the inferior oolite. 



One in the lias sandstone. 



One in the marl below the chalk. 

 Genus 70. Selaginites. Stems dichotomous, not present- 

 ing regular elevations at the base of the 

 leaves, even near the lower end of the stems ; 

 leaves often persistent, enlarged at their 

 base. 



Two species in the coal formation. 

 Genus 80. Lepidodendron. Stems dichotomous, covered 

 near their extremities by simple linear or 

 lanceolate leaves, inserted upon rhomboid 

 areolffi, lower part of the stems leafless, are- 

 olas longer than broad, marked near their 

 upper part by a minute sear, which is 

 broader than long, and has three angles, of 

 which the two lateral are acute, the lower 

 obtuse, the latter sometimes wanting. 



Several species in the coal formation. 

 Genus 81. VLodendran. Stem covered with rhomboidal 

 areolae, which are broader than long, scars 

 large, few, placed over above the other, cir- 

 cular, composed of broad cuneate scales, 

 radiating from it, common centre, and indi- 

 cating the former presence of organs that 

 were, perhaps, analogous to the cones of 

 coniferas. 



Two species in the coal measures, with, 

 perhaps, another genus Bothrodendron. 

 Genus 82. Lcpidopliyllum. Stem unknown; leaves ses- 

 sile, simple, entire, lanceolate or linear, tra- 

 versed by a single midrib, or by tliree paral- 

 lel ribs; no veins. 



Five species in the coal formation. 

 Genus 83. Lepidostrobtis. Cones ovate or cylindrical, 

 composed of imbricated scales, inserted by 

 a narrow base, around a cylindrical woody 

 axis, their points sometimes dilated and 

 recurved in the form of rhomboidal disks; 

 seed solitary, oblong, not winged, nearly as 

 long as the scales. 



Five species in the coal formation. 

 Genus 84. Cardiocarpon. Fruit compressed, lenticular, 

 heart-shaped or kidney-shaped, terminated 

 by a sharpish pomt. 



Five species in coal formation. 



M0SCI. 



Genus 85. Musciies, Stem simple or branched, fili- 

 form with membranous leaves, having scarce- 

 ly any midrib, and being sessile or amplexi- 

 caul, imbricated or somewhat spreading. 

 Two species in beds above the chalk. 



CHAKACEiE. 



Genus 86. Cliara. (Gyrogenites, Lamh.) Fruit oval or 

 splieroidal, consisting of five valves twisted 

 spu-ally, a small opening at each extremity; 

 stems friable, jointed, composed of straight 

 tubes arranged in a cylinder. 



Five species in beds above the chalk. 



ALQ^. 



Genus 87. Confemles. Filaments simple or branched, 

 divided by internal partitions. 

 Two species in the chalk marl. 



Genus 88. Fmx>ides. Frond continuous, never articu- 

 lated, usually not symmetrical or subcylin- 

 drioal, simple or oftener branched, naked, or 

 more commonly leafly, or membranous, en- 

 tire, or more or less lobcd, with no ribs, or 



imperfectly marked ones, which branch in an 

 irregular manner, and never anastomose. 



Four species in the transition rocks. 



Seven in the bitumenous strata. 



Three in the oolite. 



Eleven in the chalk. 



Eleven in the London clay. 

 PLANTS, THE AFFINITY OF WHICH IS 

 ALTOGETHER UNCERTAIN. 

 Genus 89. SigillaHa, (Rhytidolepis, alveolaria, fa\ii- 

 laria, calenaria, &e, , Sternherg.') Stem coni- 

 cal, deeply furrowed, not jointed, scars 

 placed between the furrows in rows, not 

 arranged in a distinctly spiral manner, 

 smooth, much narrower than tlie intervals 

 that separate them. 



About forty species in the coal formation. 

 Genus 90. Volkmannia. Stem striated, articulated ; 

 leaves collected in approximated dense 

 whorls. 



Tliree species in coal. 



Tliese are possibly the leaves of ealamites. 

 Genus 91. Carpoliilies. Under this name are arranged 

 all the fossil fruits to which no other place 

 is assigned. 



Fossil plants forming coal. There can be 

 no doubt but that the valuable and important 

 mineral, coal, has owed its origin to vegetable 

 bodies. On examining a seam of coal, the 

 upper layer of shale which forms the roof 

 will be found to contain innumerable im- 

 pressions of vegetable stems and leaves, most 

 beautifully and faithfully preserved. Sometimes 

 large portions of the trunks of trees are found 

 traversing the centres of the coal seam; but in 

 general, the central mass has been so compressed, 

 and has undergone such a chemical change, as to 

 obliterate almost all marks of its vegetable ori- 

 gin, and a mass of semi-crystallized bituminous 

 matter alone remains. Yet, even in this bitu- 

 minous mass, traces are occasionally to be found 

 of organized strxicture. In thin slices of the 

 three varieties of Newcastle coal, Mr Hutton 

 thus describes the appearances of organization. 

 " Each of these three kinds of coal, besides the 

 fine distinct reticulation of the original vegeta- 

 ble texture, exhibits other cells, which are filled 

 with a light wine-yellow coloured matter, appa- 

 rently of a bituminous nature, and which is so 

 volatile, as to be entirely expelled by heat before 

 any change is effocted in the other constituents 

 of the coal. The number and appearance of 

 these cells vary with each variety of coal. 

 In caking coal, the cells are comparatively few, 

 and are highly elongated. In the finest por- 

 tions of this coal, where the crystalline struc- 

 ture, as indicated by the rhomboidal form of 

 its fragments, is most developed, the cells 

 are completely obliterated. The slate coal 

 contains two kinds of cells, both of which are 

 filled with yellow bituminous matter. One kind 

 is that already noticed in caking coal, while 

 the other kind constitute groups of smaller 

 cells of an elongated circular figure. In those 



