NOTES ON THE LEPIDOCARPACEAE 557 



have not been observed. Characters other than those of the seed megaspores 

 are shown, however, so that the species is classifiable with more precision than 

 is possible when only isolated seed megaspores are present. Positive differences 

 are exhibited which may have significance of more than specific value. The 

 seeds of L. glabrum are mature, and the individual sporangia (evidently not 

 entire sporophylls) have been shed. There is no previously described species of 

 recognized lepidocarps in which shedding of mature sporangia apart from their 

 integument was possible. The number of isolated sporangia which Darrah 

 records indicates decisively that shedding of the individual sporangia was a 

 normal occurrence in this species. The only mark reported on the mature 

 sporangial seed (which in this species is equivalent only to a ripened ovule — 

 without the additional sporophyll parts possessed by seeds of other lepido- 

 carps) is at the point of its attachment to a pedicel or pedicel-equivalent. 

 Mature megasporangia (seeds) of Lepidocarpon or Illiniocarpon were not so 

 separated from their sclerous integuments. Abortive and immature sporophylls 

 of L. lomaxi commonly lack the integument, but junctional seeds are equipped 

 with them. Typical Lepidocarpon sporangia are not sclerotic but have walls 

 whose prismatic layer is strikingly similar to that of Lepidostrobus. Their 

 preservation appears primarily to result from the efficient protection of the 

 integumentary organ. 



Darrah's illustrations and description of the wall of L. glabrum sporan- 

 gia (seeds) thus suggest that they differ considerably from sporangia of the 

 lomaxi group. The unintegumented sporophylls described by Fredda Reed also 

 are noteworthy in their lack of a prismatic sporangial coat. Similar sporangia 

 of the lomaxi group described by Scott possess a somewhat thicker sporangial 

 wall tissue than the integumented forms, but the prismatic layer apparently is 

 developed typically in all. Illiniocarpon shows a different type of modification 

 in the sporangial wall. In the lower anterior region the wall is thick, and 

 although the prismatic layer is easily recognized it is considerably modified 

 and possesses larger cells with undulant walls (cf . Fig. 9; Schopf, 1938a) . The 

 anterior prongs show rather typical prismatic (columnar) structure but the 

 posterior part of the sporangium wall is more delicate and can hardly be consid- 

 ered prismatic. In fact it resembles the epidermal layer of a well protected 

 ovule. This is what would be expected if the lepidocarp sporangium were modi- 

 fied in accordance with the degree of exposure and protection afforded by the 

 integument. The adaxial ("posterior") part of the seed body in Illiniocarpon 

 is well enclosed and probably was somewhat better protected than in Lepido- 

 carpon, but the anterior part of the seed (facing the lamina) may have been 

 more exposed because the sporophyll lamina was not reflexed upwards around 

 it. Evidently the character of the sporangium wall deserves more thorough 

 study in the lepidocarps because it probably reflects the type of seminal modi- 

 fication. 



Intrasporangial tissue within the dermal layer in Lepidocarpon glabrum 

 also appears to be a significant character. In the unintegumented sporangia of 

 the lomaxi group the sporangial tissue is consistently thicker than in the integ- 

 umented seeds, and this was explained on physiological- ecological grounds. In 



