MORPHOLOGIC FEATURES 



19 



microsporangiate cones of Mazocarpon 

 are more fragmented, and the spores 

 are more or less completely dispersed. 

 Dehiscence of the microsporangia is 

 somewhat more regular than in the 

 megasporangia. A fracture occurs on 

 either side of the microsporangium 

 (corresponding to a position slightly 

 above the lateral keels of the megaspor- 

 angium) and crosses around over the 

 distal end, as shown by breaks in the 

 sporangial wall in text figures 3b and 

 3c. It is also common for the micro- 

 sporangium to separate from its pedicel 

 and split along the line of attachment. 

 It seems probable that the microspor- 

 angiate as well as megasporangiate 

 cones were intact when shed from the 

 trees which bore them and that the 

 distribution and association of micro- 

 spores with megaspores took place in 

 the surficial litter of the peat swamp. 

 Isolated microspores are very common 

 in the matrix of these Calhoun coal- 

 balls, and if wind had been an effective 

 agent in their dispersal, it does not 

 seem that the microspore concentration 

 would be so great. 



Microspores are shown at higher mag- 

 nification on plate 5, figure 4. They are 

 about 60 fi in diameter, slightly tri- 

 angular, with trilete rays extending to 

 the equator. The expospore is papillate, 

 as shown in figure 4a. The endospore 

 is thin but generally distinct. The exo- 

 spore is commonly torn when the peels 

 are removed, the endospore remaining 

 intact, as in figure 4b. The sutures are 

 carried through the endospore, and at 

 the tip of each of the endosporal pyra- 

 mic segments there is a refractive glo- 

 bule or thickened spot. This is charac- 

 teristic although its significance is un- 

 known. The endospore shows no other 

 distinctive features. 



The microsporophylls shown in figure 

 3, plate 5, seem unmistakably to be in 

 verticils. The slightly tangential sec- 

 tion of the cone apex shown at greater 

 magnification on plate 5, figure 5, il- 

 lustrates the nearly perfect symmetry 

 on either side of the cone axis. 



In contrast to Mazocarpon shorense 

 and M. petty ciirense, M. oedipternum 

 has very little sterile tissue in its ma- 

 ture microsporangia. In immature spor- 



angia a moderate amount of sterile tis- 

 sue is found, as shown diagrammatically 

 in text figure 3a from a sporangium at 

 the tip of a cone. The subarchesporial 

 pad of mature sporangia collapses into 

 an irregular line of material centrally 

 located in the sporangium which is 

 sometimes ^'T" shaped as shown in 

 figure 6, plate 4 (s). This is connected 

 to the pedicel along the line of sporan- 

 gial attachment. The walls in mature 

 microsporangia, like the walls in the 

 sporangia of most other lycopods, are 

 only a single cell-layer thick. There is 

 little if any more sterile tissue in these 

 microsporangia than in those of several 

 species of Lepidostrohus. 



The presence of the ligule is very 

 difficult to ascertain on most of the 

 sporophylls. Ligules are rarely found, 

 which is surprising in view of the abun- 

 dant and well-preserved material avail- 

 able. No ligules have yet been fou.nd 

 at the cone tip, and it is certain that 

 the ligules did not function as protec- 

 tive organs for the apical meristem, as 

 the sporophyll laminae themselves over- 

 arch the meristem and provide this pro- 

 tection (pi. 5, fig. 5). It is still possible 

 the ligule may have functioned in spore- 

 lings during germination stages. Plate 

 4, figure 7, shows what is probably the 

 shrunken vestige of a ligule (lig). The 

 distal end of this sporophyll is shown 

 at lower magnification in figure 8 and 

 is also drawn diagrammatically in text 

 figure 3b. In some megasporangiate 

 sporophylls there is a suggestion of a 

 pit distal to the sporangium which may 

 represent a place of ligular attachment. 

 However, from the evidence now at hand 

 one hesitates to say that the ligule is 

 a constant feature of either megaspor- 

 angiate or microsporangiate sporophylls. 



As previously mentioned (p. 14) the 

 sporophyll trace in the pedicel and lam- 

 ina is chiefly composed of scalariform 

 tracheids. Distal to the sporangial at- 

 tachment and above the heel, the trace 

 curves downward abruptly before it 

 turns up to supply the lamina. This 

 distal downturn of the trace has been 

 called a "dorsal loop". Inside the loop 

 the trace expands by the addition of 

 scalariform transfusion-type tracheids. 

 These are shown in figure 7, plate 4, 



