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Scientific Proceedings, Royal Dublin Societij. 



no conclusions can be drawn from it. It must be remembered, however, 

 that the lobation described is general in this one frond and is observable 

 in anotlier, and that we have scarcely a dozen fertile fronds all-told for 

 examination. The fine frond reproduced in Plate IV. shows many details of 

 structure of distinct interest. Some of these may be mentioned. The 

 sterile tip of the sporophyllule is sometimes, as seen, divided into several 

 digitiform riband-like processes. At one point in Plate IV. the whole sterile 

 pinnule is pinnately segmented into similar processes (Text, figs, 7'and 8) . This 



pinnately-lobed pinnule is highly suggestive of several species of Sphenopteris, 

 and seems to indicate that Archseopteris has within it Sphenopteris affinities. 

 There are all stages of transition in these fronds between purely sterile and 

 mainly fertile pinnules (fig. 7). Even the abaxial lobe is occasionally 

 fringed with a few sporangia. In a row of otherwise normal sporangia one 

 is enlarged, flattened, and evidently converted into a sterile segment. 

 Occasionally the abaxial lobe is itself bifurcated (fig. 1). As Archseopteris grew 

 possibly throughout the northern hemisphere in the Upper Devonian epoch, 

 in all likelihood the lobation here noted was not uncommon. Archaeopteris 

 is one of the earliest of our known land-plants, in a labile or plastic state. 

 Confine the assimilalive and reproductive functions to definite regions, 

 bifurcate the frond so that one part is vegetative and the other fertile, and the 

 origin of Botrychium from Archseopteris is not difficult to trace. Restrict 

 these two functions, reduce and simplify the output of both, and we have the 

 condition of things in Opliioglossum. 



If the fertile and sterile portions of the composite frond of Rhacopteris 



