• TRxVNSACTIONS OF SECTION K. 829 



Firth of Forth, aOords a atriking ilhistration ol" u Puheozoic plant exhibiting a 

 structure far more complex than that of any known type among existing ^'ascular 

 Cryptogams. As 8oott clearly shows in his admirahle memoir, C/icirostrohus is a 

 synthetic or compound genus, one of the numerous extinct types brouu'ht to light 

 by the anatomical investigation of fossil plants, from which we have learnt more 

 about the inter-relations of existing classes than we could ever hope to discover 

 from the examination of recent species. 



In this Scotch cone, about 8'5 cm. in diameter, we recogni.se Equi.setaceous 

 and Lycopodinous characters combined with morphological features typical of the 

 extinct genus Sji/iouop/iyllum. Some specimens of vegetative stems defscriLed by 

 Nathoi'st from Bear Lsland uoder the name Pseidlohovnia — characterised by their 

 whorled leaves with fimbriate blades borne on nodal regions separated by long 

 internodes — may, as Scott has suggested, represent the branches of the tree of 

 which C'/icimxtrobux was the cone. Both Devonian and (Julm rocks have I'urnished 

 many examples of Lycopodinous plants. The genus JJothrodcndrun, closelv allied 

 in habit to Lepiilodendron, has been recorded from Bear Island, Ireland, and 

 Australia, and the cuticles of a Lower Carboniferous .«pecies form the greater por- 

 tion of the so-called paper-coal of Tula in Russia. Lepidodeiidron itself had 

 already attained to the size of a forest tree, with anatomical features precisely 

 siuiilar to those of the succeeding Coal period species. 



Our knowledge of the ferns is not very extensive. The genus Archa-opterix 

 from Ireland, Belgium, Bear Island, and North America has always been regarded 

 as a fern, but we must admit tlie impossibility of accurately determining its syste- 

 matic position until we possess a i'uller knowledge of the reproductive organs and 

 of its anatomical structure. Similarly the genera Rhacopteris, Adiantites, and 

 Mhodea, with other characteristic members of the Lower Carboniferous vegetation, 

 may be provisionally retained among the oldest known ferns. The genus Cardio- 

 pteris — a plant with large oblong or orbicular pinnules borne in two rows on a stout 

 rachis — is known only in a steiile condition, and it is quite as likely that its repro- 

 ductive organs may have been of the Gyranospermous as of the Filicinean type. 



Renault has described under the name Todeopsis some petrified .sporanoia 

 which appear to be practically identical with those of existing Osmuudaceae, and 

 a new Devonian genus Cephalotheca has been instituted by Nathorst for iertilo 

 specimens of a strange type of plant which he refers to the Marattiacea-. Of much 

 greater importance than the sterile fernlike fronds, Avhich cannot be assigned with 

 confidence to a definite position, are the petrified remains of stems and leaves of 

 such plants as Iletirangitnn, Lytjinodendriiv, Calamopityst, and others which de- 

 monstrate the existence of a class of synthetic genera combining Filicinean and 

 Cycadean characters. These plants are of exceptional interest as showing beyond 

 doubt that Ferns and Cycads trace their descent from a common ancestry. Some 

 of the supposed ferns from Lower Carboniferous rocks are known to have been 

 fronds borne on stems with the structure of cycads, and we have good reason for 

 believing that some at least of the gymnospermous seeds of Palreozoic age are 

 those of plants of which the outward form was more fernlike than cycadean. 

 The annouricement made a few months ago by Professor Oliver and Dr. Scott that 

 they had obtained good evidence as to the connection of the gymnospermous seed 

 known as Laj/cnostoma with the genus Lyginodendron is one of the most important 

 contributions to botany published in recent years; if, as I firmly believe, the 

 evidence adduced is convincing, it gives satisfactory confirmation to suspicions 

 that previous discoveries led us to entertain. The fact demonstrated is this : the 

 genus Lyyiiiodendvim, a plant known to have existed during the greater part of the 

 Carboniferous epoch, posses.sed a stem of which the primary structure was almost 

 identical with that which characterises some recent species of Osmundacere, while 

 the secondary wood produced by the activity of a cambium is hardly distinguish- 

 able from the corresponding tissue in the stem of a recent cycad. The fronds 

 were those of a fern, both in the anatomy of their vascular tissue and in their 

 external form: as far, therefore, as the vegetative characters are concerned, we 

 have a combination of ferns and cycads. We still lack complete knowledge of the 

 nature of the reproductive organs, but it seems clear that Lyyinodendron bore 



