SPERM ATOPHYTA 59 



understood. If, as is quite possible, it is the male flower of 

 Neuropteris there was a much stronger resemblance between 

 the male and female flowers of some of the cycadofilicaleans 

 than has been supposed. Needless to say the study of such 

 forms has a primary importance because of the direct bearing 

 on vital problems of plant evolution and morphology. 



It has been estimated that the Cycadofilicales formed fully 

 half of the known vegetation of the Carboniferous coal deposits. 



Neuropteris (Fig. 186). — This is an example of one of the most 

 familiar of the fern-like fronds of the Pennsylvanian coal de- 

 posits. The leaves are very large and compound, being bi-, 

 tri-, or quadri-pinnate, with oblong leaflets which are usually 

 attached to their common stalk by a short stem. Each bears 

 k median nerve from which spring secondary ones. The leaves 

 therefore are fully fern-like in superficial appearance. That 

 Neuropteris w^as not, however, a true fern was suspected from 

 the constant absence of sporangia from the leaves and this con- 

 clusion was established by the finding of leaves of the Neurop- 

 teris type in association with cycad-like stems bearing true 

 seeds. 



Pinnules of this genus are abundant in the Mazon Creek 

 iron carbonate clay concretions. These Pennsylvanian strata 

 in Grundy County, lUinois, have in this manner preserved with- 

 out crushing and in wonderful perfection not only plant remains 

 such as Neuropteris, Pecopteris and fruits, but also crustaceans, 

 insects and fish-bones. 



Pecopteris. — Fronds much like those of Neuropteris, and of 

 simflar age, but leaflets attached to the stalk by their whole 

 width and touching one another. The small, flat-winged 

 seeds are well known in P. plunckneti. 



Lyginodendron. — Stems varying in diameter from one eighth 

 of an inch (3 mm.) up to an inch and a half (4 cm.), not branch- 

 ing, but very long, bearing many leaves. Leaves very large, 

 much divided and fern-like in appearance. 



That Lyginodendron was a climbing plant is considered likely 



