14 



ILLINOIS STATE GEOLOGICAL SURVEY 



1500/x 



q 1300/1 



I lOO/i 



900/1 



700/i 



Triletes romosus 



Triletes mamillarius 



immature megaspores 



700/i 900^ I lOO/i 1300/1 1500/i 1700/t 



SPORE BODY DIAMETER-WET 



| I lOO/i 



5 900/i 



>- 



Q 

 O 



oo 



700/i 



700/i 900/i 



I lOO/i 1300/1 1500/1 1700/1 



SPORE BODY DIAMETER-WET 



Text fig. 3. — Scatter diagrams showing the spore body dimensions of megaspores of Triletes ramosus 

 Arnold, T. mamillarius Bartlett (sensu Dijkstra), and T. brasserti Stach and Zerndt, before and after 

 drying. Line of best fit determined by eye. Shrinkage averages a little less than 20 percent. All speci- 

 mens from the Willis Coal (maceration 625 B), Gallatin County, Illinois. 



The smaller, immature spores are distin- 

 guished by a thicker wall and a more tri- 

 angular shape. Although actual size does 

 not seem to be indicative for distinction, 

 the relative proportion of one feature to 

 another may be a more satisfactory basis 

 for distinction. 



Because many megaspores have been ob- 

 served to shrink noticeably when mounted 

 dry, a preliminary investigation on the 

 amount of shrinkage was made on the 

 spores of three species: Triletes brasserti, 



T. ramosus, T. mamillarius. All these 

 specimens were well preserved, those of T. 

 brasserti abundantly represented, in a sam- 

 ple chosen from the lower part (maceration 

 625B) of the Willis Coal that had been 

 macerated in Schulze's solution in August 

 of 1945 and stored in alcohol and glycerine 

 until February 1956 when the specimens 

 were transferred to water and various meas- 

 urements were made. Each specimen was 

 transferred to a cardboard mount and al- 

 lowed to dry. The same measurements 



