. The testimony of the rocks; . last added key-stone of the erection, between these and the now, let us consider how very curious the Unks arewhich give a wonderful unity to the whole. We still findgreat difficulty in distinguishing between the foliage ofsome of even the existing club mosses and the conifers;and the ancient Lepidodendra are very generally recog-nized as of a type intermediate between the two. SimilarIntel-mediate types, exemplified by extinct families, unitedthe conifers and the ferns. The analogy of Kirchneriawith the ThinnfekUa^ says Dr. Braim, is very remarkabl
. The testimony of the rocks; . last added key-stone of the erection, between these and the now, let us consider how very curious the Unks arewhich give a wonderful unity to the whole. We still findgreat difficulty in distinguishing between the foliage ofsome of even the existing club mosses and the conifers;and the ancient Lepidodendra are very generally recog-nized as of a type intermediate between the two. SimilarIntel-mediate types, exemplified by extinct families, unitedthe conifers and the ferns. The analogy of Kirchneriawith the ThinnfekUa^ says Dr. Braim, is very remarkable,42 494 ON THE LESS KNOWN notwithstanding that the former is a fern, and that the is ranked among conifers. The points of resemblanceborne by the conifers to the huge Equiseta of the Ooliticperiod seem to have been equally striking. The poreswhich traverse longitudinally the channelled grooves bywhich the stems of our recent Equiseta are so delicatelyfluted, are said considerably more to resemble the discs of Fig. IMBRICATED STEM. {Helmsdale.) pines and araucarians than ordinary stomata. Mr. Francisdoes not hesitate to say, in his work on British Ferns, thatthe relation of this special family to the Coniferae is sostrong, both in external and internal structure, that it is FOSSIL FLORAS OF SCOTLAND. 495 not without some hesitation he places them among the fernallies; and it has been ascertained by Mr. Dawes, in hisresearches regarding the calamite, that in its internal struc-ture this apparent representative of Equiseta in the earlierages of the world united a network of quadrangular tis-sue similar to that of Coniferge to other quadrangular cellsarranged in perpendicular seiies, Hke the cells of plantsof a humbler order. The relations of the Fig. order to ferns on the one hand,and to the Coniferse on the other, are equallywell marked. As in the ferns, the venationof its fronds is circinate, or scroll-like, — theyhave in several respects a resemb
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