Frofes,s,or A. C. Seward — Floras of the Past, 507 



Las always been regarded as a fern, but we must admit tb© 

 impossibility of accurately determining its systematic position until 

 we possess a fuller knowledge of the reproductive organs and of its 

 anatomical structure. Similarly, the genera Bhacopteris, Adiantites, 

 and BJiodea may be provisionally retained among the oldest known 

 ferns. The genus Cardiopteris — a plant with large oblong or 

 orbicular pinnules borne in two rows on a stout rachis — 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 which demon- 

 strate the existence of a class of synthetic genera combining 

 Filicinean and Cycadean characters, are of exceptional interest 

 as showing beyond doubt that Ferns and Cycads trace their descent 

 from a common ancestry. The announcement 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 Lagenostoma 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 

 Lyginodendron, a plant known to have existed during the greater 

 part of the Carboniferous epoch, possessed a stem of wliich the 

 primary structure was almost identical with that which characterises 

 some recent species of Osmundaceje, while the secondary wood 

 produced by the activity of a cambium is hardly distinguishable 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 Lyginodendron bore seeds constructed on the 

 Gymnospermous plan, but characterised by an architectural 

 complexity far beyond that represented in the seeds of any modem 

 Conifer or Cycad. 



In such genera of Gymnosperms as Cordaites, Pitys, and others, 

 we have examples of forest trees possessing wood almost identical 

 with that of existing species of Araucaria, but distinguished by 

 certain peculiarities which point to a relationship with members 

 of the Cycadofilices, and suggest that Conifers as well as Cycads 

 may have sprung from a filicinean stock. 



Two facts stand out prominently as the result of a general survey 

 of what are practically the oldest records of plant-life. One is the 

 abundance of types which cannot be accommodated in our existing 

 classification, founded solely on living plants. 



The Devonian and Lower Carboniferous plants lead us away from 

 the present along converging lines of evolution to a remote stage in 

 the history of life ; they bring us face to face with proofs of common 



