106 



OHIO FOSSILS 



Fig. 273 



Alethopteris (fig. 273) has long fronds with a row of leaves (pin- 

 nules) on each side. It has a distinct midrib which reaches the edge 

 of the leaf. The leaves are long, with many secondary veins, and are 

 attached by the whole width of the base. We have several species. 



Pecopteris (fig. 274) is very similar to Alethopteris but it has 

 short leaves with few secondary veins. The genus is a common one. 



Sphenopteris (fig. 275) has leaves contracted 

 at the base, as in the next genus, but it has lobed 

 or toothed leaves whereas Neuropteris has entire 

 leaves. Sphenopteris is also represented by 

 common species. 



Neuropteris (fig. 276) has entire, oval or 

 tongue-shaped leaves which are seldom lobed. 



Several species are common. 



The name Psaronius 



V*U& 



Fig. 275 



Fig. 276 



(fig. 277) has been given to 

 stems of tree-ferns reach- 

 ing a length of about 30 

 feet and with a diameter of 

 nearly two feet. In cross - 

 section, the true stem is 

 seen to be only a few inches thick and surrounded by a thick coating of smaller "stems" which 

 are called "adventitious" roots, because they originate above ground. Partial cross -sections 

 of the adventitious roots, visible on the exterior of fossil logs and trunks, are characteristic 



of this genus. 



The parts of Psaronius that show leaf -scars are given 

 another name, Megaphyton . In it, the arrangement of 

 leaf -scars is characteristic. The larger scars are oval 

 and alternate in two rows on opposite sides of the stem. 

 Psaronius and Megaphyton are common in places in our 

 Pennsylvanian. 



Calamites (fig. 278) resembles the modern horsetail 



or scouring rush. The Pennsylvanian forms of Calamites 



were trees 50 or more feet high, with a trunk 



several feet in diameter (see fig. 28). Whorls 



of leaves grew on nodes of the younger branches. Well-preserved trunks and 



sections of branches and twigs are common in some of our Pennsylvanian beds. 



Sphenophyllum (fig. 279) is small, with swollen nodes bearing 

 whorls of triangular leaves with one toothed or rounded border. It 

 is common in some of the Pennsylvanian beds of Ohio. 



Lepidodendron (fig. 280J was a giant relative of 

 the modern club -mosses, a tree 100 feet high and 2 or 

 more feet in diameter (see fig. 6b). The genus flour- 

 ished in the Pennsylvanian and died out in the Permian. 

 Fig. 279 Tne needle-shaped or strap-like leaves were borne on 



leaf-cushions or scars which are diamond-shaped and 



spirally arranged. Stalked cones grew on the ends of smaller 



branches. Isolated cones, whose specific relationship is uncertain 



though the general alliance with Lepidodendron is well supported, 



are referred to the genus Lepidostrobus . Trunks and branches of 



Fig. 280 



