MORPHOLOGIC FEATURES 



17 



phyll above, the lower part of which 

 appears at the top of the figure. 



The slender vertical stele (which is 

 medullated in this cone) is shown in 

 figures 1 and 2 cut on a long slant in 

 the cone axis. Numerous outgoing sporo- 

 phyll traces can be seen as thin dis- 

 continuous lines mounting at a steep 

 angle in the inner cortical region which 

 is otherwise nearly devoid of tissue. 



Figures 3 and 4, plate 1, are tangen- 

 tial sections of the cone. Figure 3 is 

 from a plane quite near the cone axis. 

 The sporophyll arrangement here sug- 

 gests a low spiral phyllotaxy, but this 

 appearance may be due to a slight me- 

 chanical flexure. It is not proved that 

 the sporophyll arrangement in this group 

 of plants is inflexible; other specimens 

 seem more conclusively in favor of a 

 verticillate arrangement. The section in 

 figure 4 is taken across the sporophylls 

 just proximal to the great dorsal ex- 

 pansion of the heel. Each of the three 

 sporangia shown has separated from its 

 pedicel, in the manner also shown in 

 figure 2. At this level the pedicel and 

 its wing-like lateral extensions show con- 

 siderable irregularity in form. 



The low position of the tissue-filled 

 lateral keels of the sporangia is shown 

 on plate 1, figures 3 and 4; also on 

 plate 2,, figure 4 (SpK). Plate 4, figure 

 3, shows a sporangium with but one 

 lateral keel (Sp'K). The sporangial keel 

 turns sharply upward at the distal end 

 of the sporangium as shown in text 

 figure 2. Radial sections, as on plate 1, 

 figures 1 and 2, and plate 2, figure 2, 

 cut the keel near the apex of its distal 

 upturn and permit a somewhat better 

 visualization of this structure. 



The megaspores shown in the sections 

 previously discussed appear flattened or 

 even concavo-convex (cf. plate 1, figs. 

 1-4). Spores as shown on plate 4, fig- 

 ures 2 and 4, are cut obliquely so that 

 the proximal concavity is not shown. 

 Numerous megaspores have been iso- 

 lated from the matrix by dissolving the 

 calcite in dilute hydrochloric acid, and 

 these spores illustrate best the original 

 spore form. The proximal aspect of 

 three of these isolated spores is shown 

 on plate 2, figure 5 a-c. The trilete ap- 



paratus is seen with the three segments 

 slightly upraised and the sutures split 

 apart. Not all the apical prominence 

 is due to opening of the spores, as there 

 is a distinct natural bulge of the spore 

 coat in the apical region. In general, 

 however, the proximal surface is more 

 or less concave, despite this apical con- 

 vexity. A scaly ''ramentum" which 

 separates easily from the spore coat gen- 

 erally covers each spore. There are no 

 spines on the spore coat such as are 

 characteristic of Mazocarpon shorense. 

 The nature of the ramental cover (R) 

 is clearly shown on plate 2, figure 1, 

 where it is continuous with the intra- 

 sporangial tissue. The cell walls of the 

 intrasporangial tissue adjacent to the 

 developing megaspores have been im- 

 pregnated with waxy spore-coat mate- 

 rial and are more or less incorporated 

 in the outer part of the spore coat. 

 Thus the ramentum seen on these iso- 

 lated spores is different in origin from 

 the emphytic ornamentation usually 

 seen on lycopod megaspores. The spores 

 themselves must be considered as essen- 

 tially levigate. Surface features of iso- 

 lated spores freed of the "ramental" 

 layer are seen on careful inspection to 

 be similar to the surface features of 

 spores generally identified as Triletes 

 (Aphanozonati) reinschi. Therefore in 

 McLeansboro coals, Triletes reinschi, in 

 part, is accordingly believed to repre- 

 sent Mazocarpon oedipternum. As stated 

 in an earlier paper (Schopf, 1938) T. 

 reinschi is a generalized form and this 

 species, typically based on isolated 

 spores, probably would include several 

 species if details of the cone structure 

 could be characterized in each instance. 



Female gametophytes are present in 

 several of the spores. All cones thus 

 far discovered which contain such "via- 

 ble" megaspores are in stages of dis- 

 integration. A part of one of these 

 cones is shown on plate 4, figure 1. It 

 seems likely that gametophytes develop- 

 ed, as a rule, after the cones had dropped 

 from their parent plants and were lying 

 free in the litter of the coal swamp. 

 No kinetic mechanism can be recognized 

 which would expel the megaspores from 

 the cone or from the sporangium. The 

 prismatic layer is thin on either side of 



