6i8 THE POPULAR SCIENCE MONTHLY. 



seems probable that large nut-like fruits were produced in place of 

 spores. They are known as Sigillarias, and differ from Lepidoden- 

 drons, in addition to the characters already enumerated, in having 

 stems loss frequently branched ; the stems are also longitudinally 

 fluted like some great columns of architectural beauty and finish, and 

 between each pair of vertical ribs are now found the leaf-scars in 

 variable but always orderly arrangement (Figs. 4, 5, 6). Instead of 

 at the ends of the branches, the fruit was borne in cones, resembling 

 pine-cones, springing from the sides of the stem. The leaf -scars often 

 resemble impressions made upon wax by the old-fashioned seal, and 

 hence the name Sigillaria, or seal-tree. Great, somber, stiff, post-like 

 things they must have been, as, crowding each other in all the swamps, 

 they lifted to the sky their great, bald trunks, with scarcely any branches, 

 and nothing worthy of the name of foliage. Perhaps we should say that 

 the most important part of Sigillaria was really underground, for all the 

 old coal-swamps seem to have been traversed in every direction with 

 a perfect network of creeping subterranean or subaqueous stems, and 

 from these arose the aerial fruiting stems that we have called Sigilla- 

 ria. Such underground stems, creeping and interlacing through the 

 peat-like humus, must have formed a much-needed foundation on 

 which to support the tangled forest of vegetation that grew and accu- 

 mulated in all the quaking, boggy marshes. These creeping stems are 

 called Stigmaria, and were known for a long time as one of the most 

 abundant fossils of the coal, before their relation to Sigillaria was so 

 much as suspected. They have markings arranged something as in 

 Lepidodendron, but when wq find them undisturbed still imbedded 

 by the old soil in which they grew there arise from the center of the 

 several scars long, thread-like filaments now knoAvn as rootlets (Fig. 7). 



Almost every seam of coal has been shown to rest on a bed of 

 clay, called among miners the under-clay or dirt-bed. This clay 

 is penetrated in every direction by fossil roots with upright stumps 

 sometimes attached, and it requires no argument to show that it is an 

 old fossil forest bed the original soil in which some, at least, of the 

 coal-plants rooted and grew. This old soil has always been known to 

 be particularly rich in Stigmariae with the thread-like rootlets still in 

 place, but it was not until Mr. Binney and others discovered Sigil- 

 larian stumps arising from wide-spreading Stigmarian roots that the 

 real relations of the two forms of vegetation were perceived and ac- 

 knowledged. It is always easy to do a thing after we have been 

 shown how, and so nothing is more common now in all the coal- 

 measures, both of Europe and America, than to find the upright 

 stumps and the subterranean stems still maintaining their original 

 relative positions. 



Such, in some particulars, were the Lepidodendrons and Sigillarias 

 of the coal age. The two groups of plants differ widely in some re- 

 spects, but they are connected by a complete series of intergrading 



