294 W. Carruthers — The Forests of the Coal Period. 



possessed by the leaves whicli prevent them belonging to one well- 

 defined genus. 



Plate I. — Foliage and Fruits of Calamites. 

 1 and 2, Asterophyllites ; 3 and 4, Annularia ; 5 and 6, Sphenophyllum. 



The simplest form of leaf (Astei'ophjllites) is slender and linear, 

 with a single nerve. This can scarcely be separated from the form to 

 which the name Annularia has been given, and which differs chiefly 

 in having a larger amount of cellular tissue spread out on either side of 

 the midrib. This form has a different aspect in the fossil state from 

 the other, for its whorls of numerous broad leaves are spread out on 

 the surface of deposition, while the acicular leaves of Asterophyllites 

 have penetrated the soft mud, and are generally preserved in the 

 position they originally occupied to the supporting branch. The 

 third form (Sphenophyllum) consists of whorls of wedge-shaped 

 leaves with one or more bifurcating veins. They occur like those 

 of Annularia, spread out on the surface of the shale. 



The plan of arrangement of the three forms is the same, and 

 fruits are found associated with them which have the same general 

 appearance ; but they are so ill preserved that their internal struc- 



