4 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 463 



this manner fructifications were fossilized without major compactional flattening. 

 Plant tissues decayed for the most part, but occasionally a carbonaceous film 

 was preserved. Spores are well preserved, undistorted or collapsed, and not 

 mineral filled. The spores are pale yellow to brown, and clearing is not necessary 

 for optical study. 



Spores were mechanically removed from sporangial cavities and covered 

 with absolute alcohol for one or two minutes on a microscope slide until the al- 

 cohol was nearly, but not entirely, evaporated. In this way the air which fills 

 the spores in dried specimens was removed and the mounting medium could enter 

 the spores. Then the spores were mounted in Canada balsam mixed with xylene 

 and alcohol. For scanning electron microscopy, spores or spore masses were 

 mounted with glue on aluminum studs, exposed for 12 hours to the vapor of crys- 

 talline osmium tetroxide, and coated in vacuum, first with carbon, then with gold, 

 and again with carbon (G. E. Pfefferkorn, 1969, 1970). 



Prefix designations of specimen numbers indicate the source collections 

 and locations of materials studied: 



USNM - United States National Museum, Washington, D. C. (including Lacoe 



Collection). The National Museum is the depository of all spore slides 



prepared in this study. 

 ISM - Illinois State Museum, Springfield, Illinois (including part of Langford 



Collection) . 

 C - Carr Collection, University of Illinois Natural History Museum, Urbana, 



Illinois. 

 PP or UP - Field Museum of Natural History, Chicago, Illinois (including part 



of Langford Collection) . 



Descriptive Terminology 



The terms used for the designation of different parts of the lamina from the 

 smaller to the larger unit are: lobe, pinnule, pinna, and frond. In Stellatheca 

 the smallest ultimate laminate unit of foliage is termed a pinnule in accordance 

 with the usage by Danz6 (1956). Because the same unit may be described as a 

 lobe in other foliage specimens, a uniform designation is employed (table 1 and 

 text fig. 2) with "n" indicating the ultimate order of lateral veins, n-1 the pen- 



TABLE 1 - DESCRIPTIVE TERMINOLOGY SUGGESTED FOR STELLATHECA (AND OTHER 

 SPHENOPTERIS -LIKE FOLIAGE) . (THE ORDER DESIGNATION REMAINS STABLE 

 ALTHOUGH THE INTERPRETATION MAY VARY.) 



Order 



As applied 



Other interpretation possibility 



Axis 



Lamina 



Axis 



Lamina 



n 



lateral vein 







ultimate lateral 

 vein 





n-1 



midvein 



pinnule 





lateral vein 



lobe 



n-2 



rachis (n-2) 



ultimate 

 pinna (n- 



-2) 



midvein 



pinnule 



n-3 



rachis (n-3) 



penultimate 

 pinna (n-3) 



rachis (n-3) 



ultimate 



pinna (n-3) 



