328 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



which may belong to B ot hrodendron tenerrimwn,, appears to lack 

 sterile bracts. 



Another genus, distinguished from Bothrodendron by the surface 

 ornamentation of fine raised lines between the remote leai scars, is 

 Pinakodendron. Several species have been described, and in one, 

 P. Ohmcmni, the megasporangia were attached to the basal adaxial 

 faces of the sporophylls of the same size and form as the foliage 

 leaves, and borne on certain parts of the branches, but not terminal 

 as were most Lepidophyte cones. 



Other genera of somewhat doubtful affinity are Leptophloeum 

 in which the leaf scars are more crowded, and Omphalophloios in 

 which rhomboidal bolsters were developed. Leptophloeum occurs in 

 the Devonian or Lower Carboniferous of North America, Europe, 

 Asia, and Spitzbergen, while Omphalophloios is found in both 

 America and Europe. 



Other related forms are referred to the genus Archaeosigillarea or 

 Protolepidodendron. The most remarkable of these is a large trunk 

 from the Middle Devonian of New York shown in figure 28. The 

 actual specimen, preserved in a fine-grained blue shale, was 5 

 meters in length and 38.5 centimeters in diameter at the swollen butt, 

 and 12 centimeters in diameter at the distal end. In appearance the 

 slender arching bifurcating branches with the subulate falcate per- 

 sistent leaves gave it a weird aspect. The swollen base and tapering 

 stem indicate some secondary thickening. At the base, rootlets simi- 

 lar to those of Stigmaria are preserved. The leaf cushions at the 

 base are distant and irregular. Higher up they are in vertical rows 

 on ribs separated by angular furrows as in Sigillaria, while still 

 higher up they pass gradually into typical rhomboidal spirally ar- 

 ranged Lepidodendron bolsters. The leaf scars are in the upper part 

 of the bolsters, obovate in form or slightly cordate above, and show 

 a subcentral leaf trace scar flanked by crescentic parachnoi, with a 

 well-marked ligular pit immediately above the margin. Protolepido- 

 dendron thus unites the features of Lepidodendron and Sigillaria 

 in one synthetic type and it seems probable that the majority of 

 Devonian forms that have been referred to those two genera really 

 represent Protolepidodendron. Other species have been recorded 

 from various European Devonian localities. 



In the family Lepidodendraceae, the majority of the species 

 were tall trees reaching in some cases a height of 40 meters, with a 

 straight shaft unbranched for a long distance above the ground, 

 with a dense crown of dichotomously forked branches covered with 

 crowded masses of long narrow simple leaves spirally arranged, and 

 with large terminal cones. The leaves were ultimately shed from the 

 older portions of the trunk and the geometrically sculptured stems 

 are among: the commonest of Carboniferous fossils affording the 



