14 



MAZOCARPON OEDIPTERNUM 



DESCRIPTION OF NEW MATERIAL 



Mazocarpon Benson, ex Scott, 1909 



1909— Scott, D. H., Studies in Fossil Botany, 



2nd ed., pp. 187-8, fig. 78. 

 1918 — Benson, M., Ann. Bot., vol. 32, pp. 569- 



589, pis. XVII, XVIII. 



Mazocarpon is a group of plants rep- 

 resented typically by cones that show 

 certain histologic and morphologic fea- 

 tures. Taxonomically the genus is satis- 

 factory since the name is free from 

 ambiguity. Similar cones preserved as 

 impressions or compressions usually are 

 best referred to Sigillariostrohus since 

 ordinarily such preservation does not 

 permit the identification of Mazocarpon. 

 Mazocarpon and Sigillariosirohus are 

 not synonymous because their respective 

 diagnostic features are different, but 

 from a biological standpoint the two 

 genera overlap to an as yet undefina- 

 ble degree. Sigillariosirohus is more 

 broadly defined than Mazocarpon, and a 

 more diverse array of species is included 

 in it. It is by no means certain that all 

 species assigned to Sigillariosirohus are 

 closely related. Mazocarpon, on the other 

 hand, is unquestionably a homogeneous 

 group. It is possible that forms previ- 

 ously assigned to Sigillariosirohus may 

 eventually be referred correctly to Ma- 

 zocarpon. Mazocarpon, having the more 

 precise systematic meaning, is prefera- 

 ble to Sigillariostrohus if a situation 

 should arise in which choice is permissi- 

 ble between them. 



Scott originally published the name 

 Mazocarpon and credited it to Miss Ben- 

 son, although her more complete ac- 

 count of the genus did not appear for 

 several years. Scott stated that ''Mazo- 

 carpon [is] distinguished by the fact 

 that the megaspores in the sporangium 

 are embedded in a massive parenchyma- 

 tous tissue". This single characteristic 

 will serve to distinguish the genus, since 

 a comparable development of intra- 

 sporangial tissue is not known to be 

 present in any other group. Miss Ben- 

 son's discussion provides nearly all the 

 detailed information that was known 

 of Mazocarpon prior to discovery of the 

 present material. Both Scott (1921) 

 and Hirmer (1927) have summarized 



the information Miss Benson provided 

 and offer a few additional comments and 

 photographs of megasporangia. Both 

 LeClercq (1925) and Koopmans (1928) 

 have described Mazocarpon from the 

 Great Coal-ball horizon, in Belgium and 

 Holland respectively. 



Mazocarpon shorense, described by 

 Miss Benson in 1918 is the genotype. 



Mazocarpon oedipternum sp. nov. 

 Plates 1-6 



Heterosporous lycopsid plants, pos- 

 sessed of unisexual cones. Cones of 

 medium size, about 12 mm. in diameter 

 and 10 cm. or more in length ; pedun- 

 culate; characteristically deciduous in 

 their entirety. Sporophylls apparently 

 either verticillate, five or six to a whorl, 

 arranged in alternating series, or at- 

 tached in a low spiral. Sporophylls fair- 

 ly persistent on the cone axis. Axis 2-3 

 mm. in diameter, consisting of a narrow 

 sclerotic shell less than 200 /x thick, 

 equivalent to the outer cortex. The vas- 

 cular system is centrally placed and 

 consists of stele and sporophyll traces. 

 Only occasional bits of delicate internal 

 cortical tissues are preserved. The stele 

 is somewhat variable in diameter and 

 in structure; it varies from %-% mm. 

 in diameter and generally appears me- 

 dullated with a few scattered central 

 tracheids enclosed by prosenchymatous 

 "pith" cells; sometimes the stele has 

 little medullary tissue and appears as 

 a solid vascular strand. Traces come 

 off from it at a long slant and appear 

 to enter the fourth whorl of sporophylls 

 above their point of origin. In their 

 horizontal course through the sporophyll 

 the trace lies close to the adaxial side 

 of the pedicel ; distal to the sporangium 

 there is a well-defined dorsal loop. With- 

 in the pedicel and lamina, tracheids of 

 the trace are chiefly scalariform; in 

 the axis, spiral and annular elements 

 make up much of the sporophyll trace. 



The mega- and micro-sporangiate 

 cones and sporophylls are similar except 

 for their sporangia. The pedicel is at- 

 tached at right angles to the axis and 

 has broad thin laminal extensions on 

 either side. The bulbous dorsal ap- 



