GENUS TRILETES 



23 



1950 Lagenicula rugosa (Loose) Arnold, p. 82-85; 



pi. XI, figs. 1-4; pi. XII, figs. 1-4. 

 1955 Lagenoisporites rugosus (Loose) Potonie and 



Kremp, in Potonie and Kremp, p. 122; pi. 4, 



fig. 22. 



Discussion. — These megaspores generally 

 are subround to oval in outline, depending 

 on compressional orientation, and com- 

 monly range between 400 fx and 1100//, in 

 maximum diameter. Trilete structures gen- 

 erally are prominent, characterized by an 

 apical prominence formed by thickened ex- 

 pansions of the contact faces. Arcuate ridges 

 are commonly low but distinct; may be or- 

 namented with scattered tubercles. Gener- 

 ally the spore coat is granulose to punctate 

 or rugose, ranging between 5 ^ and 20 p in 

 thickness. A folded inner membrane is 

 commonly present. 



The spores illustrated on plate 3, figures 



4 to 9, show the range of variation that has 

 been observed during this study. The spore 

 shown in figure 4 has a thin coat (5 fx) and 

 vaguely developed arcuate ridges. A smaller 

 spore, shown by figure 6, has prominent lips 

 and arcuate ridges. Another spore (not 

 illustrated) of similar size, from the same 

 sample, bears ornamentation similar to that 

 shown by figure 5. The globular-tipped 

 papillae are up to 31 ^ in length and gener- 

 ally are concentrated in the equatorial re- 

 gion. None was observed to reach the 

 length of those reported by Chaloner 



(1953b) from cones of Lepidostrobus olryi. 



Many spores from different coal beds pos- 

 sess the scattered smaller globules described 

 by Arnold (1950), Chaloner (1953b), and 

 Felix (1954). The spores shown in figures 



5 and 8 are characteristic of the Colchester 

 (No. 2) Coal and have distinctly punctate 



coats. Others from the same coal bed are 

 heavily rugose, and some bear a distal cov- 

 ering of minute spines, more pointed than 

 those shown in figure 7. 



Spores with papillae such as are shown in 

 figure 7 are most conspicuous in the Rock 

 Island (No. 1) Coal (macerations 528A, 

 599B). Extreme rugosity of the spore coat 

 is commonly seen on some of the spores in 

 the Colchester (No. 2) Coal (especially in 

 macerations 603, 826). Those described by 



Schopf (1938) as Triletes translucens from 

 the Herrin (No. 6) Coal have a slightly 

 thicker coat than the majority of those from 

 the older coals of the Carbondale and 

 Tradewater Groups. 



I chose to describe these spores in the 

 broader taxonomic sense because no con- 

 spicuous morphological variations that 

 have not been described as occurring nat- 

 urally in the same cone were noted during 

 the study. However, a concentrated study 

 of these forms may prove that such varia- 

 tions do exist. I do not intend to imply dis- 

 agreement with Schopf's (1938) specific sep- 

 aration of some of the forms. Specific sep- 

 aration could easily be made on the basis of 

 arbitrary size limits, presence or absence of 

 papillae, size of papillae, and on the thick- 

 ness of the spore coat, but separation does 

 not seem warranted in view of present in- 

 formation on the range of variation among 

 spores found in the same cone. As Arnold 

 (1950) pointed out, factors of preservation 

 and differences in compressional orienta- 

 tion also may render specific separation dif- 

 ficult. 



Affinity.— Both Chaloner (1953b) and 

 Felix (1954) described Triletes rugosus-type 

 megaspores in association with Lycospora- 

 type microspores from cones of Lepidostro- 

 bus. Their findings support the suspected 

 close relationship between the spinose and 

 nonspinose lageniculate megaspores. As 

 the botanical relationship of lageniculate 

 megaspores with Lycospora-type micro- 

 spores is known from several cone studies, 

 it is puzzling to note the abundance of T. 

 rugosus in the Rock Island (No. 1) Coal (in 

 particular maceration 599B) concurrent 

 with the rarity of Lycospora (Kosanke, 

 1950, p. 67). 



Previously Reported Occurrences. — 

 Spores of this type have been reported by 

 Dijkstra (1946) to occur, in various coal 

 basins of the world, in the Namurian A-C 

 and in the Westphalian A-E. Because of 

 differing taxonomic circumscriptions of Tri- 

 letes rugosus, occurrences of widely differ- 

 ing age are cited in the literature. 



Occurrence. — Spores of Triletes rugosus 

 first occur, in some places abundantly, in 



