556 THE AMERICAN MIDLAND NATURALIST 



and the species was transferred to the genus Lepidocarpon (Schopf, in Janssen, 

 1940). Lepidocarpon corticosum (Lesq.) Schopf is most closely related to L. 

 novaculeatum and L. robustum both of which were transferred from Bassler's 

 genus Cantheliophorus^ which is discussed on a later page. An abortive mega- 

 spore from the original tetrad is present in its normal position near the anterior 

 of the seed body in the holotype of L. corticosum in addition to the large 

 fertile one. L. mazonense and L. corticosum furnish substantial proof that 

 histological features are not essential for recognition of this genus, and in this 

 respect Kidston's generic identification of L. westphalicum is confirmed. 



Darrah has recently described a new species under the name of Lepido- 

 carpon glabrum (1941). Although cellular detail is preserved in his specimen 

 few characters were available for distinguishing this species and consequently 

 its generic classification deserves more critical examination. This plant has 

 seeds which consist (so far as the types at least are concerned) of a sporangium 

 with well developed internal tissue surrounding the seed megaspore. No infor- 

 mation as to the pedicel, lamina, or axial attachment of the complete sporophyll 

 is provided nor is there any evidence of the integuments that characterize 

 mature seeds of all other members of the genus. 6 



llliniocarpon was distinguished from Lepidocarpon (1) because the sporo- 

 phyll was pedunculate in one and normally situated on a strobilar axis in the 

 other; (2) because in llliniocarpon the integuments are separately vascularized 

 posterior from the peduncle and are developed differently, being far more 

 evaginate; (3} the sporophyll lamina in llliniocarpon is straight and not 

 reflexed as in Lepidocarpon. (4) Apparently correlated with this last character 

 is a further specialization of the sporangium wall near the ligular region at the 

 anterior end of the seed which has not yet been found in Lepidocarpon. 



Lepidocarpon glabrum is inadequately known regarding (1) strobilar (com- 

 pact, lax) or non-strobilar habit, (2) presence, absence, or nature of the true 

 iepidocarp integument, and (3) character of the lamina. It cannot be positive- 

 ly identified -vith Lepidocarpon because these important diagnostic characters 



5 The writer is not quite certain, that Bassler's L. robuslum and L. novaculeatum 

 are specifically distinct from each other or from L. corticosum. The relationship in any 

 case is evidently very close. However there seems to be ample basis for specific dis- 

 crimination betveen the other forms Bassler described. Nevertheless, the arrangement of 

 plates and destriptne data is such that careful study of Bassler's paper is required in 

 order to clearlr establish the specific differences. 



6 Darrah las described the external layer of the sporangial wall as the "integu- 

 ment." From a purely descriptive standpoint the term may be so used, but it is inadvis- 

 able because ill other Lepidocarps have a distinct organ, called the integument by 

 most writers, tlat is entirely separate from the megasporangium. Specimens of Lepido- 

 carpon glabrun, do not now possess any integument of this sort. Whether the sporangia 

 were originally integumented when the sporophyll was complete is unknown, although 

 from Darrah's accoant it seems unlikely that they were. 



Darrah alst infers (op. cit. p. 95) that the sporangial wall of Lepidocarpon 

 includes sclerotc "protective tissues." Scott's description of specimens of the lomaxi 

 group do not stpport this conclusion and in only one form (aside from L. glabrum) 

 has sporangial w/1 sclerenchyma appeared (Reed, 1936). 



