472 Palaeontologie. 



Devonian and Lower Carb onif e ro us Floras. 



What do we know as to the composition of the floras that 

 flourished in the later stages of the Devonian and in the latter 

 part of the Carboniferous era? 



In Archaeocalamites we have the oldest example of an un- 

 doubted Equisetaceous genus. The structure of its compara- 

 tively thick and woody stem is practically identical with that 

 of our common British type of Calamites while the strobilus 

 differed in no essential feature from that of a modern Horsetail. 

 The genus Chelrostrobiis, founded in 1897 by Dr. D. H. Scott 

 on a Single specimen of a petrified cone affords a striking 

 Illustration of a Palaeozoic plant exhibiting a structure far more 

 complex than that of any known type among existing vascular 

 Cryptogams. In this Scotch cone, about 3,5 cm. in diameter, 

 we recognise Equisetaceous and Lycopodinous characters com- 

 bined with morphological features typical of the extinct genus 

 Sphenophyllum. Both Devonian and Culm rocks have furnished 

 many examples of Lycopodinous plants. The genus Bothro- 

 dendron, closely allied in habit to Lepidodendron, has been 

 recorded from Bear Island, Ireland, and Australia, and 

 the cuticles of a Lower Carboniferous species form the greater 

 portion of the so-called paper-coal of T ul a in Russia. Lepido- 

 dendron itself had already attained to the size of a forest tree, 

 with anatomical features precisely similar to those of the suc- 

 ceeding Goal period species. 



Our knowledge of the ferns is not very extensive. The 

 genus Archaeopteris from Ireland, B e 1 g i u m , Bear Island, 

 and North America has always been regarded as a fern, 

 but we must admit the impossibiüty of accurately determining 

 its systematic position until we possess a fuller knowledge of 

 the reproductive organs and of its anatomical structure. Simi- 

 larly the genera Rhacopteris, Adiantifes, and Rhodea may 

 be "provisionally retained among the oldest known ferns. The 

 genus Cardlopteris is known only in a sterile condition, and it is 

 quite as likely that its reproductive organs may have been of 

 the Gymnospermous as of the Filicinean type. 



The petrified remains of stems and leaves of such plants 

 as Heterangium, Lyginodendron, Calamopitys, and others de- 

 monstrate the existence of a class of synthetic genera combining 

 Filicinean and Cycadean characters. These plants are of ex- 

 ceptional interest as showing beyond doubt that Ferns and 

 Gycads trace their descent from a common ancestry. The an- 

 nouncement made a few months ago by Prof. Oliver and Dr. 

 Scott that they had obtained good evidence as to the connection of 

 the gymnospermous seed known as Lagenostoma with the genus 

 Lyginodendron is one of the most important contributions to 

 botany published in recentyears. We still lack complete knowledge 

 of the nature of the reproductive organs, but it seems clear 

 that Lyginodendron bore seeds constructed on the Gymno- 



