328 



PALEOZOIC TIME. 



The Asterophyllites (Fig. 638) were plants having the leaves, or 

 rather branchlets, in whorls around the jointed stems, as in Catamites ; 

 and Sphenophylla are others, like Fig. 640, with the leaf-like ap- 

 appendages broader and wedge-shaped. 



The Lepidodendrids were especially characteristic of the Lower 

 Coal-measures, as well as of the Middle and Upper Devonian. The 

 Sigillarids and Calamites abound in the Lower, but also run through 

 the Upper. The Asterophyllites belong especially to the Upper, 

 though occurring below. 



4. Conifers. — Coniferous trunks and stumps are common through 

 the Coal-measures. Cordaites are strap-shaped leaves, half an inch to 



Figs. 642-643. 



642 A 642 B 



643 



Fruits. — Fig. 642 A, Cardiocarpus elongatus ; 642 B, C. bisectus ; 642 C,C. samaraeformis. Fig. 

 643, Welwitschia mirabilis, showing transverse section of fruit, with the outline of the fruit 

 finished in dotted lines. 



an inch and a half wide, sometimes short, as in the Devonian species 

 represented on page 269, and sometimes a foot or more long. They 

 are often crowded together in great numbers in the slates overlying 

 the coal-beds, and are common in other positions, thus showing that 

 they were shed in great numbers by some plants of the era. They 

 have been referred both to the Lepidodendrids and to the Cycads, 

 and by Schimper are embraced in Brongniart's genus Pycnophyllum^ 

 under the latter order. Geinitz has observed, in Saxony, and, later, 

 Newberry, in Ohio, the winged fruits of the genus Cardiocarpus 

 (Figs. 642 A, B, C) associated with the leaves of Cordaites; and 

 both have regarded it as highly probable that the fruit and leaves 



