42 THE OLDEE MESOZOIC FLOEA OF VIEGINIA. 



This plant is one of the finest and most interesting in the coal field. 

 I have been enabled to obtain a large number of well preserved specimens 

 of it, which show its very polymorphous nature and the many peculiari- 

 ties presented by it. In the first place the fructification presents a very 

 different aspect according as the upper or under surface of the pinnules, or 

 the imprints of these, are seen. The imprints of the upper surface of the 

 fructified pinnules, or the upper surface itself, present the form given in 

 Plate XXIII, Fig. 1. This figure represents the imprint of the upper sur- 

 face of the fructified pinnules of large size, and Fig. 2 the imprint of the 

 same surface of the lobed pinnae of the lower portion of the plant. It will 

 be noticed that the sori appear here as elongated swellings, occupying the 

 place of the lateral nerves. They have the general character of the fructi- 

 fication usually assigned to the fossil genus Asplenites. The sori, however, 

 are really round, as may be seen when the under side of the pinnules is 

 presented to view with the leaf-substance preserved, and have the character 

 described. The peculiar elongation shown when the upper side or its 

 imprint is seen is caused by the fact that the rounded sorus and its strong 

 nerve, when pressed against the thick, dense leaf-substance of the pinnules, 

 do not present a sharply defined outline of the separate parts when seen 

 from the upper side, but the sorus and nerve produce a club-shaped promi- 

 nence in which the sorus occupies the thickest part. I think that the same 

 thing would happen when any thick coriaceous pinnules were pressed down 

 upon a yielding substance like shale with its lower surface in contact with 

 the shale. Hence many of the apparent elongated sori of the type of Asple- 

 nites may really be rounded. Plate XXIII, Fig. 4, represents the imprint 

 of the under side of the large fructified pinnules, and gives the termination 

 of one of the pinnse. Plate XXII, Fig. 2, gives the form presented by pin- 

 nules, which are fructified only at the ends. The rest of the pinnule has the 

 usual nervation and other characters of the lai'ge sterile pinnules. This 

 specimen had all the leaf substance of the plant preserved, and showed the 

 under side of the pinnules with the sori. Plate XXIV, Figs. 1 and 2, rep- 

 resent forms in which the pinnules are more remote than in the normal 

 forms. They may belong to a variety of Asterocarpus Virginiensis, suffi- 

 ciently distinct to be separated as such; but as the plant in question shows 



