ON COAL. 169 



in the general structure of its wood, and to the Cryptogams in the 

 venation of its leaves. If there was no other evidence we might he in 

 douht as to its true position ; but the simplicity of its reproduction 

 and of its tissues settles the question, as it seems to me, forever. 

 There are other points of alliance between pines and club-mosses, 

 which it would lead me too far to notice. In fact this family seems 

 to be, in a remarkable degree, both a connecting and an embryonic 

 type, and therefore, as we shall presently see^ eminently calculated 

 to throw light upon the plants of the coal. 



Let us now attempt to apply these principles in the interpretation 

 of the plants of the Coal, and particularly of the four families already 

 taken as representatives of the flora of this period, viz: the Ferns , 

 Sigillarice, Lepidodendron, and Calamites. We shall confine our atten- 

 tion principally to the second and third. With reference to the 

 Fertis there is little dispute ; their unmistakable resemblance to the 

 ferns of the present flora leave no doubt as to their afiinities. I will 

 only remark, in passing, that many of the coal genera of this family 

 seem to have affinities also with the Cycadce and Coni/erce. With 

 reference to the other three families the difficulty is much greater^ 

 they are generally supposed, however, to be most nearly allied to the 

 Lycopodiacece (club-mosses) and the Equisetacece, (horse-tails ;) the 

 Sigillarice and Lepidodendrons being considered most nearly allied to 

 the club-mosses, and the Calamites to the horse-tails. If so, then we 

 are at once struck with the enormous size of the coal plants in com- 

 parison with their humble representatives at the present day. Sigil- 

 larice and Lepidodendrons attained the amazing height of seventy to 

 one hundred feet, and a diameter of five to six feet, while the club- 

 mosses of the present day seldom rise to an altitude of more than a 

 few inches. Calamites attain a diameter of fourteen or fifteen inches, 

 and a height of thirty to forty feet, while the horse-tails are among 

 our humblest plants. This enormous difference in size is sufficient of 

 itself to lead us to suspect that these are not true club-mosses and 

 horse-tails. Let us examine them more closely. 



Here you have rude sketches of these families. This is Sigillaria. 

 This genus is so little known as to its external appearance that I 

 cannot represent or speak of it with any confidence. In almost every 

 case it is ibrmed as a straight cylindrical trunk, without branches or 

 leaves. So that, although this plant is so common, yet its mode of 

 branching and the form of its leaves is still a matter of dispute among 

 botanists. In a few cases Sigillaria trunks have been found to bifurcate 

 and produce long cylindrical branches. In a single, perhaps doubt- 

 ful, case {Sig. Icpidodendrifolia) leaves have been found similar to 

 Lepidodendron. One of two views seems probable : either that many 

 so-called Lepidodendrons, so commonly found in connexion with 

 Sigillaria, are the branches of the latter, in which case the branching 

 and foliage of this genus are similar to tbe Lepidodendron, or else 

 that Sigillaria, like tree ferns, were generally branchless, and that the 

 large fronds, (generally supposed to belong to Ferns,) which are po 

 commonly found strewed in profusion about their bases, were their 

 leaves. What I have represented by these sketches are therefore 

 ideal restorations on the former hypothesis, rather than actual speci- 



