A CONTRIBUTION 

 TO THE KNOWLEDGE OF THE RELATION 

 BETWEEN PSILOPHYTON AND RHYNIA. 



(From the Botanical Laboratory of the 

 Groningen University) 



by 



G. POSTHUMUS. 



With one plate. 



In 1871 the Canadian palaeontologist Dawson (1871, 

 1888), found in rocks of Devonian âge of his native country 

 some plant-remains, which by their habit showed a close 

 resemblance to some marine Algae. Thèse 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 présence of a central bundle, 

 composed of scalariform tracheides. He considered Psilo- 

 phyton 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 hâve had a 

 widespread distribution. In many cases the deposits in 

 which they occurred showed marine faciès. This fact and 



