Johnson — Spermolithus Devonicus and other Pteridosperms. 247 



in considering the affinities of A. hibemica. It reaches its extreme develop- 

 ment in the sterile pinnules of. A. fimbriata Nathorst, of the Devonian of 

 Bear Island. S. (A.) Tschermaki has a bifurcate pinnate frond. The pinnae 

 are more or less oblong and lobed, but are not divided into pinnules. The 

 basal pinnae may be basally pinnatisect. W. Gothan does not appear to 

 attach due importance to this degree of segmentation, since in his valuable 

 work on the coal plants of Upper Silesia he speaks of Sphenopteridium 

 Dawsoni Stur sp. as standing nearest to, if not identical with, S. Tschermaki 

 (which is itself allied to Heterangium), yet S. Dawsoni has a typical bifurcate 

 bipinnate frond with distinct obovate lobed pinnules. If these marked 

 differences in the degree of segmentation of a frond are to be regarded 

 as of no systematic value, many names of fossil species must fall. Even 

 in Archaeopteris proper the species are ill-defined and insufficiently 

 illustrated. It is, in consequence, difficult to contrast satisfactorily A. hiber- 

 nica with Dawson's many American species. It would be a distinct advantage 

 to have a revised photographic untouched-illustrated account of these species 

 for comparison with those of Bear Island, Kiltorcan, and the continent of 

 Europe. 



The search at Kiltorcan has brought to light many specimens of fertile 

 fronds of Archaeopteris hibemica showing the general characters, now well 

 known. The fertile pinnule represented in fig. 1, PL XI, is new and of 

 considerable interest. Several such were found, but always in a detached 

 state, until that shown in fig. 2, PL XI, was observed, enabling me to refer 

 the structure to Archaeopteris hibemica. 



The stalked palmatisect wedge-shaped pinnule is seen divided into two 

 segments, each of which is again divided. The four lobes carry on their edges 

 normal stalked sporangia. The cauloid position of the fan-shaped pinnule 

 (fig. 2, PL XI) is interesting, though not surprising, as the simple pinnules 

 inserted on the rachis between the pinnae are a generic character of 

 Archaeopteris. So far I have failed to find anything indicative, as I hoped, 

 of the conversion of a stalked sporangium into a seed. Examination of the 

 contents of the sporangia has not as yet shown any signs of a differentiating 

 heterospbry tending towards a distinction into seeds and microspores. Up to 

 the present the only kind of spore found is that shown in fig. 3a, PL XI, in 

 surface view, and in b in optical section. The spore is spherical, 50 /a in 

 diameter, and shows a pitted wall, suggestive of numerous possible pores of 

 dehiscence. I have, however, found many slabs covered in patches or streaks 

 with minute black bodies. These are generally isolated, but are sometimes 

 stalked. Sometimes the stalk is forked, and occasionally curved or spirally 

 coiled. The dark bodies occur singly, now and then apparently paired. They 



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