154 PKOCEEDIKGS Oi' IHE GEOLOGICAL SOCIETY. 



ably resemble Cycads in the structure of their stems. Their long 

 rigid narrow leaves may be compared to single pinnae of the leaves 

 of Cycads. Their cord-like rootlets, as I have ascertained by actual 

 comparison, are similar to those of Cycads. If their fruit was of the 

 nature of Cardiocarjnim or Trigonocarpum, this also would corre- 

 spond. They differed principally in the division of the stem below 

 into those remarkable underground branches, the Stigmarice, and in 

 the great upward extension and, in some instances at least, ramifi- 

 cation of the stem. The former may be regarded as a special modi- 

 fication connected with their peculiar habitat. The latter may be 

 interpreted as a modification either tending backward to the Lycopo- 

 diacese or forward to the Coniferse. Since, so far as we at present 

 know, the ramification prevails chiefly in the lower forms, the 

 former may be the more correct view. It is even possible that the 

 BigiUarice may include forms bridging over the space between the 

 higher Acrogens and the Gymnosperms. ^Viewed in this way, the 

 typical ribbed Sigillarice point downwards through Ccdamodendron 

 and Calamites to the Equisetacea?, and the Favidaria- and Clathraria- 

 types point \ihxQVL^Lepido])liloiosn.i\diLepidodendron toLycopodiaceai. 

 In the upward dii'ection their affinities j)oint both towards Conifers 

 and Cycads. As our knowledge of the structure of individual species 

 of Sigillaria increases, we may hope more certainly to trace the links 

 of these affinities. It is, however, to be observed here, by way of 

 caution, (1) that, of the plants reckoned among the several genera or 

 subgenera of Sigillarice, some may eventually prove to be gymno- 

 spermous and some cryptogamous, and (2) that, as we shall find in 

 the next group to have been actually the case, some of these plants 

 may, with a cryptogamous fructification, have presented a structure 

 of stem more complex than that found in modem plants of similar 

 grade. 



2. CALAMODEifDEoisr and Calamites. 



Calamites are among the most abundant fossils of the Carboni- 

 ferous period, and occur also in the Devonian ; and from their pecu- 

 liar habitat and mode of growth, they are not only preserved as 

 flattened stems, but also occur in immense numbers standing on the 

 beds on which they grew. 



They have naturally been regarded from the first as aUied to 

 Equisetacece ; and this opinion is ably and, indeed, conclusively 

 maintained by Schimper in his recent Avork*, and has been illus- 

 trated by the recent description of the fruit by Mr. Carruthers. 

 Dif&culties have, however, arisen from the fact that some stems 

 regarded as Calamites have been found to be surrounded by a thick 

 woody cylinder composed of discigerous and pseudo-scalariform 

 tissue, similar to that of the typo of SigUlaria above described. 

 Some botanists have regarded these last as distinct from the true 

 Calamites, and have placed them in the genus Calamitea, Cotta, or 

 Calamodendron, Brongniart ; and Williamson has recently proposed 



* Pal6ontologie V^g^tale. 



