40 



ILLINOIS STATE GEOLOGICAL SURVEY 



of the apical prominence. Potonie also 

 stated (1954b): 



Par contre [to the Bothrodendraceae], on sait 

 que les Lepidodendraceae ne portent jamais de 

 fimbriae ramiferes. 



As discussed in the general comments 

 preceding the discussion of lageniculate 

 megaspores, the morphological distinction 

 between the megaspores of the Lepidoden- 

 draceae and Bothrodendraceae, based on 

 apical development and spine configura- 

 tion, although valid for megaspores of 

 upper Mississippian and Pennsylvanian 

 age, is apparently not applicable to mega- 

 spores of lower Mississippian age. These 

 older megaspores possess modified charac- 

 teristics of the megaspores of both families. 



The microspores of cones allied with the 

 Bothrodendraceae are, as yet, unknown. In 

 the present investigation, an intimate as- 

 sociation of megaspores of the Triletes glo- 

 bosus-type with the small spores of Denso- 

 sporites was noted, particularly in the coal 

 in the Hardinsburg Formation and the 

 Reynoldsburg Coal. It would seem that 

 these megaspores and small spores may be 

 either botanically related or may have been 

 borne by plants with similar ecological re- 

 quirements. The stratigraphic occurrence 

 of Densosporites is compatible with either 

 possibility. Densosporites (Kosanke, 1947, 

 fig. 1) is represented abundantly in Casey- 

 ville coals, present in coals of the lower part 

 of the Tradewater, sporadic in occurrence 

 in those of the upper part of the Trade- 

 water, and apparently absent from younger 

 coals. 



Paralleling the occurrences of Denso- 

 sporites, the megaspores of the Triletes 

 globosus-type are characteristic of and 

 abundant in Caseyville coals, present spo- 

 radically, at places in abundance, in Trade- 

 water coals up to and including the Rock 

 Island (No. 1) Coal, and apparently ab- 

 sent in coals in the upper part of the Trade- 

 water and in younger coals. That Denso- 

 sporites is abundant in the Mississippian 

 Hardinsburg Formation is known from 

 both the work of Hoffmeister, Staplin, 

 and Malloy (1955) and from my own 

 observations. 



In opposition to this relationship, either 

 botanical or ecological, abundant spores of 

 Densosporites occur in a Springer or Ches- 

 ter coal described by Schemel (1950a) , but 

 are not accompanied by spores of Triletes 

 globosus or T. hirsutus. In addition, these 

 megaspores also are apparently absent from 

 the sample of Tarter Coal that contained 

 sporangial masses of Densosporites. How- 

 ever, recently Chaloner (1958a) described 

 microspores of the Densosporites-type and 

 megaspores of the T. hirsutus-type from the 

 cone of Selaginellites canonbiensis Chalo- 

 ner, presumably borne by a herbaceous 

 plant. 



Some measurements of selected previous- 

 ly described megaspores and of the Triletes 

 hirsutus-type and T. globosus-type de- 

 scribed here are presented in table 1. None 

 of the spores described here is considered 

 at present identical to any of those from 

 European coals designated as T. hirsutus 

 (Loose) Schopf, Wilson, and Bentall. 

 Rather they are considered to be most 

 closely related to those of T. globosus Ar- 

 nold described from the Michigan Basin 

 or given varietal status under T. globosus. 

 Consequently it seems advantageous to dis- 

 tinguish them from European forms rather 

 than to form conclusions, possibly unjusti- 

 fied, regarding their affinity. Potonie and 

 Kremp (1955) consider T. globosus as dis- 

 tinct from Setosisporites hirsutus. 



I feel that the differences in ornamenta- 

 tion, some slight, between spores typical of 

 Triletes globosus, T. globosus var. (A) , T. 

 globosus var. (B) , T. globosus var. (C) , 

 and T. cf. T. hirsutus are botanically and 

 stratigraphically significant. Two general 

 statements regarding the Illinois T. glo- 

 bosus-type spores are possible: 1) many of 

 the megaspores from coals in the upper 

 part of the Caseyville are identical to those 

 originally described by Arnold as T. glo- 

 bosus; 2) no megaspores found, as yet, in 

 Illinois coals appear to possess spines as 

 long as or as ramose and antlerlike as were 

 illustrated by Potonie and Kremp (1955, p. 

 123, fig. 37; pi. 4, figs. 25, 27, 29a, 29b) for 

 Setosisporites hirsutus (Loose) Ibrahim. 



Although there may be some confusion 

 between spores of Triletes globosus var. 



