A contribution to the knowledge of the relation between Psilophyton and Rhynia

In 1871 the Canadian palaeontologist Dawson (1871, 1888), found in rocks of Devonian age of his native country some plant-remains, which by their habit showed a close resemblance to some marine Algae. These plants were named Psilophyton, Psilophyton princeps being the best known species. This plant possessed slender erect stems, springing from a creeping rhizome, and covered with numerous projecting, often recurved spines, which are often wanting on the thinner branchlets. They were dichotomously forked. The occurrence of sporangia at the top of the ultimate branchlets could be established. Besides this Dawson succeeded in demonstrating the presence of a central bundle, composed of scalariform tracheides. He considered Psilophyton to be a Pteridophyt, chiefly from this characteristic, though in its habit and in the situation of the sporangia it showed a departure from this group. Afterwards this and allied forms were found in several places, in France, Germany, Bohemia, Norway, etc., in Devonian strata. At that period they seem to have had a widespread distribution. In many cases the deposits in which they occurred showed marine facies. This fact and their habit being so different from that of the Pteridophyta and more resembling some of the Phaeophyceae, lead to the supposition that the views held by Dawson were erroneous and that Psilophyton belonged to the Sea-weeds. This view has lately been supported by Pohlig (1916, p. 225).