MAZOCARFON AND SIGILLARI08TR0BUS 



31 



figs. 1 and 8).^^ This also suggests an 

 alliance with Lepidostrohus rather than 

 with Sigillariostrohus, since lagenicnlate 

 megaspores have their known relation- 

 ship with the former group. 



Some of the microspores reported 

 from S. spheno'phylloides are ex- 

 ceptionally large (85 ft). Others, sup- 

 posed to be immature, are about 35 /x 

 in diameter. The former exceed those of 

 Mazocarpon in size but the latter are 

 small enough to match those of Lepidos- 

 trohus. Conclusive information on the 

 morphology of the microspores might 

 be of considerable value in identifying 

 the genus, but apparently Miss Le- 

 Clercq's material did not macerate very 

 well and the characters are not clearly 

 defined on any of the microspores shown. 

 The sporophylls of 8. sphenophyl- 

 loides were caducous as in several other 

 species of Sigillariostrohus and in Mazo- 

 carpon shorense. However this is of 

 little or no diagnostic value because 

 caducous isolated sporophylls of Ortho- 

 lepidostrohus (Arber 1922, p. 173) are 

 at least as abundant as those of Sigil- 

 lariostrohus, Mazocarpon, or other 

 genera. 



For these various reasons it may be 

 concluded that Sigillariostrohus spheno- 

 phylloides LeClercq is not conclusively 

 identified as to genus and hence should 

 not be relied upon for evidence relating 

 to cones of Sigillariostrohus. The cone 

 probably belongs to Lepidostrohus in- 

 stead, and the occurrence of bisexuality 

 in it may not be as unique a feature as 

 was supposed. It is from beds of lower 

 Pennsylvanian age, and whether it is 

 particularly related to verticillate Lepi- 

 dostrohus of the Lower Carboniferous 

 is not clear. 



No other reports of bisexual cones of 

 Sigillariostrohus are known to the au- 

 thor. It seems that there is little trust- 

 worthy evidence that bisexual cones oc- 

 curred in the sigillarian alliance, par- 

 ticularly during Pennsylvanian time. 

 There is likewise no evidence of bi- 

 sexual cones occurring in Mazocarpon. 

 Miss Benson assumed that cones of 



"Megaspores which are at least very closely 

 related to Triletes (Lagenicula) Mdstoni Zerndt 

 have been isolated from Caseyville coals of the 

 Illinois basin and also from thin Mississippian 

 coals in the upper part of the Chester series. 



Mazocarpon shorense were bisexual, but 

 this was supported by no direct evi- 

 dence. So far as the evidence goes, 

 again there is no apparent disparity 

 between Mazocarpon and Sigillariostro- 

 hus in regard to unisexuality of the 

 cones produced. Records of microspo- 

 rangiate cones of Sigillariostrohus are 

 so largely inferential that this apparent 

 agreement cannot be given undue 

 weight at present. Nevertheless, it seems 

 most likely that unisexual microsporan- 

 giate cones of Sigillariostrohus will be 

 proved if an adequate study is under- 

 taken. 



The cones of some Lower Carbonifer- 

 ous (Mississippian) sigillarians may 

 have been typically bisexual because 

 the unisexual cones of Mazocarpon must 

 be taken as quite highly specialized 

 and as derived from a more primitive 

 condition. At some point in the sigillar- 

 ian ancestry the cones must have been 

 bisexual. Only a few species of modern 

 Selaginella (cf. Mitchell, 1910) attain 

 similar specialization among the living 

 lycopods. Nevertheless, unisexual cones 

 are quite in keeping with other features 

 of Pennsylvanian sigillarians which have 

 been mentioned, such as the pedunculate 

 mode of fructification, specialization of 

 the gametophyte, characteristics of the 

 megasporangium, etc., all of which ex- 

 ceed the modern forms so far as relative 

 structural modification is concerned. 



One of the strongest sources of evi- 

 dence indicating the alliance of Sigil- 

 lariostrohus and Mazocarpon is in the 

 megaspores themselves. These are suf- 

 ficiently large and abundant in Sigil- 

 lariostrohus cones to have been noted by 

 several observers. The megaspores in 

 general are those which the author has 

 previously concluded must be classified 

 together in the aphanozonate section of 

 Triletes. This decision originally was 

 based on a comparative study of spore 

 morphology. It was recognized that the 

 presence or absence of apiculae was a 

 character of importance only for spe- 

 cific discrimination, and megaspores re- 

 ported from cones of Sigillariostrohus 

 strongly tend to confirm this view. In 

 most descriptions of Sigillariostrohus 

 species the spore characteristics are not 

 fully reported, and there is some ques- 



