24 



MAZOCARPON OEDIPTERNUM 



that spores were produced in pockets of mas- 

 sive intrasporangial tissue. The single micro- 

 sporophyll found was evidently immature 

 since the spores were still in tetrads. Tissue- 

 filled sporangial keels are present. These 

 features and the association of this speci- 

 men with megasporangiate material in coal- 

 balls from Shore, Lancashire, are the basis 

 for assigning it to Mazocarpon shorense. 



The features of the megasporangiate 

 cone of Mazocarpon shorense (text fig. 

 5c) and of a similar cone of M. oedipter- 

 num (text fig. 5b) have been incorpor- 

 ated in diagrammatic longitudinal sec- 

 tions for direct comparison. Besides the 

 great difference in thickness of the axial 

 outer cortex and in length of their re- 

 spective sporophyll laminae, the divers- 

 ity in spacing of sporophylls may be 

 noted. M. shorense is here depicted with 

 the sporophylls in a ''close spiral" and 

 the distal "convex cushion" (heel) 

 close above the sporangium below. The 

 sporophylls of M. oedipternum are more 

 widel}^ and alternately spaced. Wide 

 spacing of the sporophylls is apparently 

 connected with formation of the large 

 dorsal heel of M. oedipternu-m. No 

 causal explanation for this phenomenon 

 can be advanced at present. The heel 

 serves to make the cone more rigid (as 

 it does in Lycopodium cernuiim, see 

 Lang, 1908) but if the sporophylls were 

 more closely mounted on the axis, as in 

 M. shorense, presumably the same de- 

 gree of rigidity would be achieved with- 

 out a dorsal heel. 



There seems to be little essential dif- 

 ference between the megasporangia of 

 M. shorense and M. oedipternum. The 

 latter species, however, lacks the up- 

 standing ventral pedicel ridge which 

 attaches the sporangium of M. shorense. 

 In the new species the vascular trace 

 runs close to the top of the pedicel for 

 part of its length but can not be said 

 to leave the pedicel. Thus far no vas- 

 cularization of the base of the sporan- 

 gium has been noted such as was re- 

 ported for Mazocarpon cashii and in 

 lesser degree for M. shorense. Conse- 

 quently, no additional support is given 



the sporangiophoric interpretation once 

 advanced by Miss Benson (1908). The 

 centrally located intrasporangial tissue 

 in the megasporangium of M. oedipter- 

 num, which may be compared with the 

 subarchesporial pad of modern lycopods, 

 shows a slight alignment of cells radiat- 

 ing from the base. This may be a result 

 of growth of intrasporangial tissue in 

 the direction of the nutritional gradient 

 while the young sporangium was active- 

 ly enlarging. 



The levigate megaspores of Mazocar- 

 pon oedipternum are distinct from the 

 apiculate spores of M. shorense. Proba- 

 bly of greater significance is the fact 

 that more than one archegonium may 

 be produced within a single megaspore 

 of the English species. M. oedipternum 

 has been found in about a dozen in- 

 stances to have only a single very large 

 archegonium placed directly below the 

 spore apex. This is a rather surprising 

 constancy in a character which is vari- 

 able in modern forms. Although it is 

 a member of the Paleozoic flora it seems 

 more advanced and specialized in this 

 feature than either modern Selaginella 

 or Isoetes. The large size of the arche- 

 gonia also is probably a specialized fea- 

 ture. The gametophyte and archegonia 

 are far better preserved in M. oedipter- 

 num than are those from any other 

 Paleozoic form now known. 



The microsporangiate cones of M. 

 oedipternum are considerably different 

 from those ascribed to M. shorense. They 

 differ little from microsporangiate por- 

 tions of cones of Lepidostrohus, the 

 chief specific distinction apparently be- 

 ing the broad lateral laminae of the 

 pedicel in Mazocarpon oedipternum ; the 

 pedicel of Lepidostrohus sporophylls is, 

 in comparison, very contracted. The 

 microspores of both M. oedipternum 

 and M. shorense are exceptionally large 

 for lycopod microspores. Whether fea- 

 tures other than size are similar is in- 

 determinable at present because the M. 

 shorense microspores were all in tetrads 

 and lacked their mature ornamentation. 



