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At the present time a very considerable amount of progress is being 
made in palaeontological Botany by the careful comparison of specimens 
with each other, and the revelations brought to light by the microscope of 
their minute vegetable structure. 
Fossil plants are traced back even to the Silurian System, that is, the oldest 
of the sedimentary rocks, the Palgechorda, an Alga much like Chorda filum of 
our times, has been detected in abundance iu the Lower Silurians. In the 
Old Eed Sandstone series of rocks, Fucoids and other Algae have been 
found. Cyclopterus Hibernicus occurs in the Yellow Sandstone of the south 
of Ireland, included in the Old Red period. In the Carboniferous series 
commencing with the Millstone Grit, Calamites are plentiful, and Stigmaria 
that is the roots of Sigillaria, whose trunks formed a large portion of that 
mineralized vegetable matter called Coal. In the Coal Measures vegetation 
appears to have reigned supreme, for pure Coal is vegetable matter 
condensed. Sphenopteris, Calamites, and Lepidodendron, were types of 
plants analogous to the Ferns, Equisetums, and Lycopodiums, of the 
present day. Lepiclodendra were great plants of the Club-moss type, 
that rose seventy feet high. It was of course an absolute mechanical 
necessity, that if they were to present, by being tall and large, a wide front 
to the tempest, they should also be comparatively solid and strong to resist 
it, and such on examination is found to be the case. In attempting to 
picture to himself the dense green web of vegetation that covered the face 
of the earth at the time of these Old Carboniferous deposits, the 
Palaeontologist imagines himself walking in the dark aisles of Nature's 
Cathedral, where the slim columns vrere fretted over with ara' sque 
tracery t some sixty or seventy 1 br nching off in., an ile<2 <nt 
network of filagree, or headed with a capit J of feathery foliage like the 
palm trees of the tropics of the present day, or darkening with their clouds 
of cone-like fruits the already misty and vapoury face of the earth. 
In the Oorruu formation a new feature of vegetation presents itself in the 
form of Zamia, allied to the Cycads of the present time. 
The whole of the foregoing Fossils are included in the classes of A crogens 
and Grymnogens, and almost the whole of known fossils belong to the 
natural order Filices, Lycopodiacae. Equisetacese, Cyeadacese, or Coniferae. 
Among the more recent discoveries made in this department of science, those 
made by Mr. William Carruthers, of the British Museum, are most 
important. Of the Genus Lepidodendron he says, "That they are 
numerous in species, and very numerous in individuals, any one who has 
cursorily examined a coal-pit, or the fossils in any public museum, must 
