MAZOCARPON AND SIGILLABIOSTROBUS 



29 



Diode of fructification, a characteristic 

 whose importance has been emphasized ^ 

 There are certain other features which 

 also must be more or less definitely 

 included in the diagnosis of this genus 

 but none of them seem entirely essential. 

 The cones are of medium to large size. 

 The sporophylls are often apparently 

 in verticils and, so far as is known 

 now, they appear to be unisexual. The 

 megaspores appear to agree with those 

 of the Aphanozonati section of Triletes. 

 In Schimper's original description of 

 Sigillariostrohus (1870) he assumed that 

 the smaller of the spores were micro- 

 spores although they were about a milli- 

 meter in diameter. Consequently he 

 considered the cones of Sigillariostrohus 

 heterosporous. Several authors have 

 commented that all the spores described 

 by Schimper are probably megaspores, 

 and this is apparently the case because 

 features of even the smallest of the 

 spores he mentions agree with known 

 megaspores, and of all the lycopod mi- 

 crospores known none exceed 1/10 the 

 diameter of the ''microspores" Schim- 

 per observed. 



So far as size and general habit 

 characteristics are concerned, the cones 

 of Sigillariostrohus are not different 

 from Mazocarpon. The cones of Mazo- 

 earpon thus far described are all smaller 

 than the largest of Sigillariostrohus 

 species, but the majority show marked 

 similarity if allowance is made for dif- 

 ferences in preservation. 



Bochenski (1936, p. 230) has suggest- 

 ed that verticillate arrangement of 

 sporophylls (in addition to their ped- 

 unculate characteristic) may also be a 

 diagnostic feature of Sigillariostrohus. 

 There is probably a much greater ten- 

 dency towards verticillate arrangement 

 in both Sigillariostrohus and Mazocarpon 

 than in Lepidostrohus. This character 

 cannot be considered diagnostic however, 

 since Zeiller (1914) reports a verticillate 

 arrangement of sporophylls in Lepidos- 

 trohus hroivnii, and Binney (1871) has 

 also illustrated specimens which are ver- 



ticillate. Verticillate arrangement in 

 Lepidostrohus is harder to establish than 

 in Sigillariostrohus or Mazocarpon be- 

 cause the orthostiches commonly ap- 

 pear to be more numerous. Still in the 

 lepidostrobid forms mentioned, there 

 seems no occasion to doubt that the 

 sporophylls are in verticils.^ All these 

 are from the Lower Carboniferous^ 

 which may be a point of some signifi- 

 cance. Most Pennsylvanian species of 

 Lepidostrohus seem to have a spiral 

 phyllotaxy. But in any event there is 

 no direct relationship apparent either 

 between verticillate species of Lepidos- 

 trohus and verticillate species of Sigil- 

 lariostrohus or between Lepidostrohus 

 and Mazocarpon. It is therefore im- 

 possible to consider this character of 

 essential diagnostic significance. 



It should also be pointed out that a 

 low spiral phyllotaxy may, under some 

 conditions of preservation, simulate ver- 

 ticillate arrangement or vice versa. The 

 arrangement of sporophylls reported 

 for Mazocarpon shorense may easily be 

 as "verticillate" as some specimens of 

 Sigillariostrohus in which a whorled 

 phyllotaxy is confidently reported. Even 

 if the possibility of error in determina- 

 tion of phyllotaxy in Sigillariostrohus 

 is discounted, the possibility of devia- 

 tion from a strictly whorled to a low 

 spiral arrangement of sporophylls must 

 always be borne in mind when dealing 

 with this group of plants. Specimens of 

 Mazocarpon oedipternum are illustrated 

 which may represent both types. How- 

 ever, so far as phyllotaxy is concerned, 

 Mazocarpon and Sigillariostrohus here 

 have no points in significant conflict. 



There is considerable evidence that 

 cones of both Mazocarpon and Sigillari- 



TKidston (1911 p. 182) has considered the 

 Ulodendron condition of Clathrarian sigillarians 

 indicative of the presence of sessile cones in this 

 section (in part) ; Sigillaria discophora which he 

 cites is placed by several authors in the separate 

 genus Ulodendron, and in any event Watson (1914) 

 has shown that Ulodendron type scars are not 

 caused by sessile cones. 



^Species of Bothrostrotus are also described as 

 verticillate. 



^Hirmer (1927, p. 230) says Lepidostrohus 

 'broicnii is from the middle Upper Carboniferous 

 but this is an error. The geologic position of 

 several noted specimens of L. hroivnii (including 

 the holotype) is unknown because they were sec- 

 ondarily "derived from glacial deposits. Zeiller 

 (1914) gives the age of several specimens whose 

 source is known, as lower Dinantian, i.e., the 

 lower part of the Lower Carboniferous, and Read 

 and Campbell (1939) suggest that some of them 

 may possibly even be from beds of uppermost 

 Devonian age. The source of L. fischerl, Scott and 

 Jeffrey, (the name later changed to Lepidostrohus 

 kentucki/ensis by Scott because "fischeri" was pre- 

 occupied) also is listed erroneously by Hirmer : 

 this species comes from the New Albany shale 

 which Read and Campbell (1939) believe also is 

 uppermost Devonian. 



