Internally, the structure of the trunks was similar to that of modern pine trunks. Casts of the pith are referred to the genus Artisia. The seeds were borne in clusters on branches in leaf axils.
The Cordaites were major contributors to some coal beds.
FRUITING BODIES
([Plate 5])
Fossils representing many kinds of plant reproductive structures are found in Pennsylvanian rocks, but unfortunately most of them are not attached to any identifiable part of the parent plant and they cannot be assigned definitely to a particular plant. Such fossils are referred to genera and species solely on the basis of their own characteristics, although, as in other fossil classifications, such “form genera” are presumed to be parts of, or related to, the plants with which they are found in habitual association.
A few such fossils, fairly common in Illinois, are illustrated on [plate 5] to show their general shape and size. When attached to an identifiable leaf or leaflet, the seed is referred to as the seed of that leaf genus.
For example, Holcospermum, a radially symmetrical seed with ribs and grooves, Codonotheca, a stalked, spore-bearing, lobed “cup,” and Neuropterocarpus, a flask-shaped seed with longitudinal ribs and grooves, all have been associated with Neuropteris, a leaf genus.
Mazon Creek Strip Mine Area Showing Distribution of Spoil Heaps. The small circular areas represent waste from underground mines.
Trigonocarpus, commonly found as a cast of the internal part of a seed, is a trimerously symmetrical body frequently associated with Alethopteris. Pachytesta includes preserved structures and outer layers of a seed. Carpolithes is a catch-all “genus” functioning as a general term for seeds and seedlike forms whose plant group affinities cannot be determined.