FRUCTIFICATIONS FROM THE MAZON CREEK FLORA 



21 



Genus SCOLECOPTERIS Zenker, 1837 



Two specimens from Mazon Creek, Illinois, tentatively assigned to Scole- 

 copteris , were examined and spores were extracted. In both specimens the en- 

 tire lamina of each pinnule appeared to be covered with spores. Macroscopically 

 the two specimens appear to be similar. The specimens used are: 



? Scolecopteris sp. 1 C 10800 



? Scolecopteris sp. 2 C 10803 



Macroscopic Description.— Pinnules are tongue-shaped and Pecopteris - 

 like. They taper slightly towards the top and near the base. The midvein is thick 

 and lateral veins are simple or forked once (text fig. 7). Subsidiary veins are 

 probably present. Sterile pinnules are 5 mm long and 3 mm wide, and the midvein 

 (visible only in specimen C 10803) is 0.3 mm wide. Fertile pinnules are 5 to 9 

 mm long and 3 to 3.5 mm wide. Pinnules touch each other at the margin and are 

 attached to the pinna axis at an angle of 70°-90°. The margin of fertile pinnules 

 is strongly curved abaxially. 



The pinna is about 6.5 cm long, 17 mm wide in the middle, and 12 mm 

 wide at the base, and bears about 22 pinnules on each side. The pinna axis is 

 1 . 8 mm wide and has a weak and irregular longitudinal striation and stout hairs 

 which are 0.2 mm thick at their bases (text fig. 8). Fructifications cover the en- 

 tire under-surface of fertile pinnules. Each fructification is 1.4 mm long and 0.4 

 mm broad, extends nearly to the margin of the pinnule, and has a longitudinal 

 striation vertically oriented to the midvein. Single sporangia are not discernible 

 in the two specimens. 



? Scolecopteris sp. 1 

 pi. 12, figs. 3, 4, 5, 6 



Description.— The spores (specimen C 10800) are trilete and circular to 

 subcircular in transverse plane. Laesurae are distinct and straight, and two of 

 the laesurae generally form almost a straight line and are about equal in length to 

 the spore radius; the third laesura is perpendicular or almost perpendicular to the 

 other two and up to one-half their length; minor folds are usually present along 

 the two longest rays. The spore exine is laevigate and 1 to 1.5 |im thick. The 

 spore diameters (40 specimens) range from 16 to 23 i-im, with an average of 19 |im. 



Comparison. — If found dispersed, the spores of C 10800 would be classi- 

 fied as Puncta ti s porite s ; however, no dispersed species of Punctati s pori te s that 

 could be correlated with these spores were noted, and spores similar to those 

 of C 10800 have not been recognized in macerated rocks from the Illinois Basin. 



Text fig. 7 - Sterile pinnule of ? Scole- 

 copteris spec. 2. 



Text, fig 



Fertile pinnule of ? Scole- 

 copteris spec. 2. 



