KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 57. N!0 I. 31 



The sporiferous zone continues round the whole periphery of the upper part of the 

 capsule in a dome-shaped manner, and thus covers the third zone, which can be distin- 

 guished in the section as a central column or columella. This central part, which has a 

 breadth of about one third of the whole diameter of the capsule, is lighter coloured than 

 the sporiferous zone, as seen in surface illumination, but is almost quite opaque and is 

 not pierced by holes. It shows no structure, and was evidently composed of some deli- 

 cate sterile tissue. The petrification does not seem to have penetrated right in to the 

 centre, as there is here an irregular empty space. The limit between the central column 

 and the sporiferous zone is not very marked: it is best seen in fig. 26. The central column 

 seems to be fairly well defined against the sterile basal part of the capsule (fig. 26). 



Morpholoirical nature and relations. 



There can be no doubt that the plant-remains described above find their nearest 

 analogy in the sporogonia of the Bryophyta: whatever their systematical position may 

 be, they must be regarded as sporogonia. If compared in detail with the sporogonia of 

 the Bryophyta they are found, however, to present a combination of characters not found 

 in the sporogonia of the present representatives of that phylum. Among the sporogonia 

 of the various groups of the Bryophyta, those forms may first be excluded in which the 

 capsule is sessile or is only borne upon an elongated pseudopodium formed by the parent 

 gemetophyte. In our form it is evident that the capsule and the long, well-developed 

 seta are closely connected and both form parts of the sporophyte. Not only is the stalk 

 of a firm texture - which is proved both by the aspect of the impression and by the 

 thickness of the carbonized remains of it sometimes preserved - - but it passes insensibly 

 över into the capsule, and the striation in the basal part of the capsule continues down 

 into the upper part of the stalk. The Devonian sporogonium therefore cannot be referred 

 either to the Marchantiales, or to the Jimgermanniales, the Sphagnales or the Andraeales. 

 The whole habit is further so different from that of the sporogonium of the Anthocero- 

 tales that a comparison with this group appears too far-fetched. The whole aspect of 

 the fossils and especially the well-developed seta clearly suggest the sporogonia of the 

 Bryales as the most closely related structures among recent plants. The difference, 

 however, is important. In the Devonian fossil, the zone of sporogenous tissue is dome- 

 shaped and continues up över the columella, whereas in the Bryales it is cylindrical, 

 open at the top. To this may be added that there is no trace of any operculum as devel- 

 oped in the stegocarpic mosses, although, as already described, there is a curious thicken- 

 ing of the wall in the apical part which is as yet unexplained. It is not known how the 

 dispersal of the spores was effected: it is possible that the marked furrows in the wall of 

 the sporogenous part of the capsule may indicate a longitudinal dehiscence as in the 

 Andraeales, but there is no direct evidence on this point. 



As a summary of the preceding discussion it may be stated that Sporogonites exu- 

 berans must be regarded as a sporogonium comparable to that of the Bryophyta, but that 

 it does not fall within the limits of any of the existing groups of that phylum. For the 

 present it may be regarded as a generalized type, presenting certain points of agreement 

 with different groups of Bryophyta and therefore as a possible starting point for develop- 



