36 



ILLINOIS STATE GEOLOGICAL SURVEY 



sional orientation, up to 2170 /x in total 

 diameter. Spore body round to subtriangu- 

 lar in outline, probably originally some- 

 what spheroidal, ranging from 735 to 1600 /x 

 in diameter (mean 1230 ^ for 64 specimens, 

 89 percent of which measure more than 

 1000 /a) . Trilete rays prominent, extending 

 onto flange, sometimes to outer margin of 

 flange, so that ray extremities may project 

 as points beyond spore body on an other- 

 wise denuded spore. 



Lips may be open, generally about 150 ^ 

 in height at apex (range 67 to 250 ^) , de- 

 creasing in height outward, but increasing 

 to more than apex height near spore body 

 margin. Lips straight to sinuous; upper 

 edges membranous, fluted, ornamented 

 with parallel-sided acuminate spines up to 

 30 [a in length and 15 fx in diameter. Con- 

 tact area as a rule smooth, especially on 

 smaller spores, sometimes tuberculate (pi. 

 9, fig. 4a) , equalling in diameter 80 to 95 

 percent of the spore body diameter. 



Base of encircling flange extending 

 proximal to and slightly distal to geomet- 

 rical equator so that proximal surface of 

 flange sometimes broader than distal sur- 

 face of flange, up to 240 jx in thickness (pi. 

 9, fig. 5) . Flange extending away from 

 spore body from 62 to 568 ^, generally wid- 

 est opposite trilete rays. Flange appearing 

 smooth and somewhat leathery, sometimes 

 pleated or striate proximally (pi. 9, figs. 6, 

 7) , rarely, even minutely, fenestrate. Distal 

 surface of flange appearing spongy or 

 coarsely granular (pi. 9, fig. 4b) . By trans- 

 mitted light flange appearing beaded or 

 set with barlike processes at margin, and 

 appearing to consist of imbricated and 

 fused rod-shaped processes distally (pi. 9, 

 figs. 9, 10) . In some specimens round proc- 

 esses up to 30 jx in diameter adjacent to 

 distal surface of flange. Flange rather easily 

 detached from spore body. Completely de- 

 nuded specimens not tuberculate in zone 

 of flange attachment, showing only slightly 

 indented zone of attachment. 



Spore coat generally from 42 to 83 /x 

 thick, thickest at juncture of spore coat 

 and flange, thinnest at contact areas. Spore 

 coat on small specimen as little as 26 fx 

 thick. Inner membrane generally present. 



In some specimens inner membrane orna- 

 mented with hemispherical tubercles 6 to 

 10 ix in diameter, spaced about 25^ apart 

 (pi. 9, figs. 8a, 8b) . Spore body deep red- 

 dish brown, flange reddish orange to yellow 

 by transmitted light. Spore body brown to 

 black, upper surface of flange brown to 

 black and glossy by reflected light. 



Discussion. — Some smaller megaspores, 

 for example, the one shown on plate 9, fig- 

 ure 7, occur with the larger spores and 

 might be interpreted as Triletes subbras- 

 serti Arnold. They are rare and associated 

 only with numerous larger spores of T. 

 brasserti, at least in the Illinois coals ex- 

 amined. No distinct size limit is applicable 

 because specimens of intermediate sizes 

 also occur. At present the small spores are 

 interpreted as immature spores of T. bras- 

 serti rather than as representing a distinct 

 species. 



One of the larger specimens possessed a 

 distal membrane about 10^ thick extend- 

 ing from the distal surface of the flange. 

 The membrane is ornamented with irregu- 

 larly shaped low tubercles so closely spaced 

 as to effect a reticulate appearance. Similar 

 distal coverings have been noted for some 

 small spores of Triletes superbus from a 

 coal from another area. 



In the description I noted that these 

 spores apparently had no preferred com- 

 pressional orientation. This may be more 

 apparent than real. Many spore tetrads of 

 Triletes brasserti are present in some of the 

 samples and, if the spores were compressed 

 while in tetrad association, then dissociated 

 during maceration, no compressional ori- 

 entation would be apparent. 



Spores of this species were measured wet 

 and then dry. The scatter diagram given in 

 text figure 3 indicates the amount of 

 shrinkage, averaging about 19 percent. Not 

 only does the spore body shrink on drying, 

 but the width of the flange as well as the 

 height of the lips decreased, either be- 

 cause of shrinkage or because of slight crin- 

 kling upon dessication. Unfortunately no 

 measurements of spore coat thickness be- 

 fore and after drying were possible. All the 

 measurements given in the description are 

 those of wet or balsam-mounted specimens. 



