450 THE CARBONIFEROUS SYSTEM. 



that these curious trees were allied to ferns, and bore two rows of large 

 fronds, the trunks being covered with coarse hairs or small aerial roots. 

 At one time I was disposed to suspect that they may have crept along 

 the ground ; but a specimen from Sydney shows the leaf-stalks pro- 

 ceeding from the stem at an angle so acute that the stem must, I think, 

 have been erect. From the appearance of the scars it is pi-obable that 

 only a pair of fronds were borne at one time at the top of the stem ; 

 and if these were broad and spreading, it would be a very graceful 

 plant. To what exteut plants of this type contributed to the accu- 

 mulation of coal I have no means of ascertaining, their tissues in the 

 state of coal not being distinguishable from those of ferns and Lyco- 

 podiacese." 



3. Lycopodiacece. 



1. Lepidodendron, Sternberg. — This genus is one of the most common 

 in the Coal formation, and especially in its lower part. Any one who 

 has seen the common Ground-pine or Club-moss of our woods, and who 

 can imagine such a plant enlarged to the dimensions of a great forest 

 tree, presenting a bark marked with rhombic or oval scars of fallen 

 leaves, having its branches bifurcating regularly, and covered with 

 slender pointed leaves, and the extremities of the branches laden with 

 cones or spikes of fructification, has before him this characteristic tree 

 of the coal forests, — a tree remarkable as presenting a gigantic form of 

 a tribe of plants existing in the present world only in low and humble 

 species. Had we seen it growing, we might have at first mistaken it 

 for a pine, but the spores contained in its cones, instead of seeds, and 

 its dichotomous ramification, would undeceive us ; and if we cut into its 

 trunk, we should find structures quite unlike those of pines. As in 

 Sigillai'ia, we should perceive a large central pith, and surrounding this 

 a ring of woody matter ; but instead of finding this partly of disc- 

 bearing wood cells, as in Sigillaria, and divided into regular wedges 

 by medullary rays, we should find it a continuous cylinder of coarser 

 and finer scalariform vessels. Outside of this, as in Sigillaria, we 

 should have a thick bark, including many tough elongated bast fibres, 

 and protected externally by a hard and durable outer rind. The 

 Lepidodendra were large and graceful trees, and contributed not a 

 little to the accumulation of coal. Several attempts have been made 

 to divide this genus. My own views on the subject are given below. 



Of this genus nineteen species have been recorded as occurring in 

 the Carboniferous rocks of Nova Scotia. Of these, six occur at the 

 Joggins, where specimens of this genus are very much less abundant 

 than those of Sigillaria. In the newer Coal formation, Lepidodendra 



