656 



HISTORY OK TIIK VEGETABLE KINGDO.M. 



rows, not leaving dear and well defined 

 scars. 



Ten species in the coal formation. 



One in the inferior oolite. 



One in tlie lias sandstone. 



One in the marl below the chalk. 

 (lenns 79. Sdaginitcs. Stems diohotomous, not present- 

 ing regular elevations at the base of tlie 

 leaves, even near the lower end of tlie stems; 

 leaves often persistent, enlarged at tlieir 

 base. 



Two species in the coal formation. 

 Genus 80. Lepidodendnm. Stems dichotomous, covered 

 near their extremities by simple linear or 

 lanceolate leaves, inserted upon rhomboid 

 areola;, lower part of the stems leafless, are- 

 ola longer than broad, marlied near tlicir 

 upper part by a minute scar, wliich is 

 broader than long, and has tlirec angles, of 

 which the two lateral are acute, the lower 

 obtuse, tlie latter sometimes wanting. 



Several species in the coal formation. 

 Genus 81. XJlodendron. Stem covered with rhomboidal 

 areola;, Avhieh are broader than long, sears 

 large, few, placed over above tlic otiier, cir- 

 cular, composed of broad cuneate scales, 

 radiating from a common centre, and indi- 

 cating tlie former presence of organs that 

 were, perhaps, analogous to the cones of 

 conifera;. 



Two species in the coal measures, with, 

 perhaps, another genus Bothrodendron. 

 Genus 82. IjcpidophjUum. Stem unknown ; leaves ses- 

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

 versed by a single midrib, or by three paral- 

 lel ribs; no veins. 



Five species in the coal formation. 

 Genoa 83. Lepidostrobm. 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 rliomboidal disks; 

 seed solitary, oblong, not winged, nearly as 

 long as the scales. 



Kivo species in the coal formation. 

 Genus 84. Cardiocarpm. Fruit compressed, lenticular, 

 heart-shaped or kidney-shaped, terminated 

 by a sharpish point. 



Five species in coal formation. 



MUSCI. 



Genus 85. Musclies. 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. 



CIIABACE.E. 



Genus 86. C7«jra. (Gyrogcnites,/^mi.) Fruit oval or 

 spheroidal, consisting of five valves twisted 

 spirally, a small opening at each extremity; 

 stems friable, jointed, composed of straight 

 tubes arranged in a cylinder. 



Five species in beds above the chalk. 



AI,G^. 



Ocnufl 87. Gmfermle.!!. Filaments simple or branched, 

 divided by internal partitions. 

 Two species m the chalk marl. 



Genus 88. Fuandes. Frond continuous, never articu- 

 lated, usually not symmetrical or subeylin- 

 diioal, 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. 



FUeveu in tlie London clay. 

 PLANTS, THE AFFINITY OF WHICH IS 

 ALTOGETHER UNCERTAIN. 

 Genus 89. Su/illaria. (Khytidolepis, alvcolaria, favu- 

 laria, calenaria, &c. , Sternberg.) Stem coni- 

 cal, deeply furrowed, not jointed, sears 

 placed between the furrows in rows, not 

 arranged in a distinctly spiral manner, 

 smooth, much narrower than the intervals 

 that separate them. 



About forty species in the coal formation. 

 Genus 90. Volkmmmia. Stem striated, articulated ; 

 leaves collected in approximated dense 

 whorls. 



Tliree species in coal. 



These arc possibly the leaves of calamitcs. 

 Genus 91, CarpolUhes. Under this name are arranged 

 all the fossil fruits to which no other place 

 is assigned. 



Fossil plants formixg 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 scam; 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 scmi-crystallizcd bituminous 

 matter alone remains. Yet, even in this bitu- 

 minous mass, traces are occasionally to be found 

 of organized structure. 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 effected 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 crj-stalline 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 



