16 



ILLINOIS STATE GEOLOGICAL SURVEY 



no spores of well established species of Tri- 

 letes are less than 300 ^ in size. Some 

 spores, for example those of T. superbus, 

 are as much as 4100 ^ in over-all diameter. 



The genus is believed to represent a nat- 

 ural grouping of heterosporous free-sporing 

 lycopsids, somewhat equivalent to a sub- 

 order in the normal classification. 



Potonie and Kremp (1954, 1955, 1956) 

 believed that Triletes is an invalid and ille- 

 gitimate generic designation and therefore 

 redefined and re-emphasized some of Ibra- 

 him's (1933) generic names and established 

 new genera to which they referred mega- 

 spores. The confusion arose because of a 

 mistaken but consistent attribution of the 

 generic name Triletes to Reinsch. Triletes, 

 implying relationship with the lycopods, 

 was used by Bennie and Kidston in 1886 in 

 describing megaspores, although not in 

 combination with specific epithets. It was 

 in the sense of Bennie and Kidston's usage, 

 not Reinsch's, that Bartlett (1929) and 

 Zerndt (1930c) applied it in binomial com- 

 bination to megaspores. In 1930 Zerndt re- 

 ferred some of his specimens to those first 

 described by Bennie and Kidston. Bennie 

 and Kidston should be considered the effec- 

 tive authors of Triletes which became vali- 

 dated no later than 1930 by Zerndt's publi- 

 cation. 



Laevigatisporites (Ibrahim) Potonie and 

 Kremp (1954) , therefore, is a later synonym 

 of Triletes. The use or nonuse of the ge- 

 neric names adopted or initiated by Po- 

 tonie and Kremp is a taxonomic decision 

 to be made at present by each individual, 

 depending on his interpretation of the 

 taxonomic circumscription of Triletes. 

 Such decisions also must be made at the 

 species level. Dijkstra (1946) has inter- 

 preted some species as having a wide range 

 of spore variation, an interpretation con- 

 firmed in certain instances by cone studies, 

 whereas other authors advocate a narrow 

 circumscription about the holotype speci- 

 men. The individual acceptance of a broad 

 or narrow circumscription can be expressed 

 in the taxonomy by use of such a term as 

 "sensu Dijkstra." If each author clearly 

 states his intent and adequately describes 



and illustrates his material, future modifica- 

 tion, which always comes with expanded 

 knowledge, will be relatively simple. 



Schopf (1938) proposed the following sec- 

 tional divisions of Triletes based on com- 

 parative spore morphology: Aphanozonati, 

 Lagenicula (Bennie and Kidston), Auricu- 

 lati, Triangulati. The spores referred to 

 any one section are believed to be more 

 closely related to one another than to spores 

 referred to other sections. Such a classifica- 

 tion attempts to indicate the phylogeny and 

 natural plant relationships as closely as is 

 possible on the basis of available evidence. 



Dijkstra (1946) proposed the use of the 

 section Zonales (Bennie and Kidston) be- 

 cause he believes that some of the zonate 

 spores are not closely allied to those typi- 

 cally referred to the section Triangulati. In 

 addition, he proposed that the auriculate 

 spores should be grouped with the aphano- 

 zonate spores, rather than segregated in a 

 separate section. 



In the present paper, spores of Triletes 

 are referred to the following sections: La- 

 genicula, Aphanozonati, Auriculati, Zo- 

 nales, and Triangulati. 



Sectio Lagenicula (Bennie and Kidston) 

 Schopf, 1938 



Spores of the Lagenicula section of Tri- 

 letes are generally medium-sized, more or 

 less prolate originally, and typically later- 

 ally compressed, possessing an apical prom- 

 inence formed by the elongated and up- 

 raised portions of the three contact faces. 

 Arcuate ridges are commonly developed, 

 but extreme zonal appendages are lacking 

 (Schopf, 1938). Spore coat is variable in 

 thickness with a smooth to spinose surface. 

 Spores of T. horridus and T. rugosus are 

 typical of this section. Lageniculate spores 

 have been found in Lepidostrobus fructifi- 

 cations (Chaloner, 1953b; Felix, 1954) in 

 association with Lycospora-type micro- 

 spores, a lepidodendrid alliance. 



Potonie (1954b) stated that the mega- 

 spores of the Lepidodendraceae never bear 

 "fimbriae ramiferes" as do those of the 

 Bothrodendraceae (Triletes praetextus, for 

 example). However, there is a tendency for 



