Thirty-four species of Lepidodendron are enumerated in M. Ad. Brongniart's Catalogue of fossil plants of the coal formation.
The internal structure of the Lepidodendron has been shown to be intermediate between Lycopodiaceaa and Coniferæ,[1] and the conclusions which Prof Lindley draws from the intermediate condition of this curious extinct genus of fossil plants, are in perfect accordance with the inferences which we have had occasion to derive from analogous conditions in extinct genera of fossil animals. "To Botanists, this discovery is of very high interest, as it proves that those systematists are right, who contend for the possibility of certain chasms now existing between the gradations of organization, being caused by the extinction of genera, or even of whole orders; the existence of which was necessary to complete the harmony which it is believed originally existed in the structure of all parts of the Vegetable kingdom. By means of Lepidodendron, a better passage is established from Flowering to Flowerless Plants, than by either Equisetum or Cycas, or any other known genus." Lindley and Hutton's Fossil Flora, vol. ii. page 43.
Sigillaria.[2]
Besides the above plants of the Coal formation which are connected with existing Families or Genera, there occur many others which can be referred to no known type in the vegetable kingdom. We have seen that the Calamites take their place in the existing family of Equisetaceæ; that many fossil Ferns are referable to living genera of this extensive family; and that Lepidodendra approximate to living Lycopodiaceæ
