KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 57. NIO |. 27 



The constant association of Dawsonites with Psilophyton princeps in thrcc different 

 localities would seem to speak in favour of the possibility that both forms represent 

 different parts of the same kind of plant, but a comparison of the specimens hardly lends 

 any support to this view. It is probable that Dawsonites may be related to some of the 

 bifurcating branches of Hostimella-type described by other authors under the name 

 of Psilophyton princeps but it can hardly belong to this species as here defined. None of 

 our specimens of Psilophyton princeps shows the characteristic striation seen in the main 

 branches of Dawsonites, and not even the thickest of the latter have any spines or spine- 



scars. 



It is more probable that Dawsonites may belong to the form here described as Psilo- 

 phyton Goldschmidtii , but even of this there is no proof. 



The morphological nature of the specimens of Dawsonites is still obscure. They 

 have been spöken of here as branch-systems without any attempt to decide whether the 

 main branches are of stem-nature or represent rachises of a much-divided frond. The 

 lateral branches appear to be placed in a distichous manner, but this feature is not very 

 marked. The supposed sporangia of all our specimens are perfectly flattened and some- 

 what suggestive of pinnules, but Da\vson's descriptions and specimens from Gaspé 

 which I have examined prove that they were hollow structures. 



Sporogonites exuberans Halle. — Pl. 3. figs. 11 — 32. 



Sporogonites exuberans, Halle 1910, p. 79, text-fig. 1. 



The most interesting of the plant -remains at Röragen is a form which closely resem- 

 bles a sporogonium. It has already been described by the author in a short notice 

 accompanied by somewhat diagrammat ic drawings in the »Botaniska Notiser». In this 

 description a short diagnose is given, but for this may be substituted the following some- 

 what amplified diagnose resulting from the continued examination of the material: 



Spore-producing body consisting of a simple stalk and a terminal capsule. Stalk 

 0,5 mm. in diameter and up to at least 50 mm. long, faintly striated longitudinally. Cap- 

 sule elongatedly obovoid or clavate, 6—9 mm. long and 2 — 4 mm. in diameter in the 

 thickest part, with a rounded apex and a tapering base, gradually merging into the 

 thicker upper part of the stalk. Basal part of the capsule with probably 12 elevated 

 striae passing över into the stalk. The thickest part of the capsule with probably 12 

 longitudinal furrows of varying strength, half of the number being broader and deeper 

 than the othcrs, and the two kinds regularly alternating. The lower part of the capsule 

 sterile throughout, the upper part consisting of three different zones: a wall of several 

 layers of cells, a thick sporogenous tract, and a sterile central columella. Sporogenous 

 tract forming a complete dome covering the top of the columella. Spores tetrahedral 

 — globular, O.020 — 0,o-2ö mm. in diameter, with a cutinized wall showing a fine dotted 

 sculpture. 



