12 



PALEOZOIC FOSSIL SPORES 



see a remarkable similarity in size, form 

 and texture, sufficient to justify us in 

 supposing that the latter may be of the 

 same nature as the former, but deprived 

 of their outer cases either by dehiscence 

 or decay, and this is the view which we are 

 now disposed to take of their nature. This 

 better accords with their wide distribution 

 in aqueous deposits and with their ac- 

 companiment than any other supposition. 

 Plausible and satisfactory as this sup- 

 position may be, there is nevertheless 

 scant basis for assuming all the various 

 sporangite bodies to have such an origin, 

 not to mention the insidiousness of at- 

 tempting to apply scientific nomenclature 

 on the basis of such a supposition. It can- 

 not be said that Dawson ever proved the 

 identity of bodies within and outside the 

 "sporocarps" ; furthermore, no one else 

 has ever provided any conclusive evidence. 

 Evidently many have taken this important 

 point for granted, however, because the 

 two names are used practically inter- 

 changeably in much of the subsequent 

 literature. 



The "spherical and oval sacs, the walls 

 of which are composed of a tissue of 

 hexagonal cells . . . three to six mil- 

 limeters in diameter," apparently are 

 properly assignable to Prolosahiiiia Daw- 

 son, 1884. We are unable to ascertain 

 their characteristics reliably from any 

 figures Dawson published but White and 

 Stadnichenko (1923) give photographs 

 and data on a form, Protosalvinia raveiina 

 White, 1923, which is confirmatory of 

 their thalloid characteristics, although 

 White regarded them as sporangia. White 

 (p. 239) has repeated the suggestion, 

 (which seems to have originated with 

 Dawson, 1871a, b) that their affinity was 

 probably with "Devonian types antecedent 

 to the Carboniferous Lepidodendra and 

 Sigillariae." Possibly he thought the spor- 

 angite bodies were actually spores of 

 lycopod relationship, as many others 

 have, and he probably accepted their sup- 

 posed relationship with Protosalvinia be- 

 cause of close association. Oval speci- 

 mens of Protosalvinia bear some resem- 

 blance to lycopod sporangia, but there are 

 general objections to such an interpre- 

 tation. Even when they are occasionally 

 in abundance no cones or actual lyco- 

 podiaceous remains are noted in the same 

 assemblage (Dawson reported some du- 



bious lycopod stem material, but no thalli 

 or "sporangia" with the "spores" at Kettle 

 Point). White seems to have made no 

 close study of the sporangite forms under 

 appropriate magnification and he found 

 none of them actually in any of the multi- 

 tudinous "spore cases" (thalH?) of Pro- 

 tosalvinia which were examined. In fact, 

 although an uncritical reader may infer 

 from this work that ''Sporangites' belongs 

 to Protosaknnia, White actually made no 

 direct statement to this effect and he pos- 

 sibly had no strong convictions as to their 

 nature. As the association of thalloid 

 bodies with sporangite forms is by no 

 means common and as the sporangites that 

 have been reported differ considerably 

 (one of the generic types here being 

 treated as Tasmanites), it is evident that 

 Protosalvinia and Sporangites cannot be 

 in any way accurately treated as syn- 

 onyms. No one yet has furnished tangible 

 evidence of the nature of the spore-like 

 bodies Dawson reported actually within 

 the Protosalvinia thalli, so it still is quite 

 speculative whether any relationship 

 (other than that of a common environ- 

 ment) is evidenced by their infrequent 

 association in the Devonian-Mississippian 

 black shale. 



Dawson reviewed the subject in con- 

 nection with his paper in the bulletin of 

 the Chicago Academy of Science in 1886 

 (pp. 105-118), calling attention to Orton's 

 (1882) discovery of 6^. huronensis-Vik^ 

 bodies in the Ohio shale, Clark's (1885) 

 description of somewhat similar material 

 in the Devonian of New York, the report 

 of Johnson and Thomas (1884) on these 

 microscopic discs in the Chicago water 

 supply and glacial till of the region, New- 

 ton's (1875) description of Tasnianites 

 punctatus, and his own (Dawson, 1884a, 

 b) descriptions of two lots of Brazilian 

 material sent him by Hartt and by Orville 

 Derby. He makes no direct mention 

 either of the Joggins specimens or of 

 ''Sporangites'' acuminata. This article is 

 the best of any written by Dawson on the 

 subject. Nevertheless, in it, as well as 

 in his other papers, the inadequacies of his 

 concepts are fully apparent. He appears 

 confused as to the distinction between 

 spores and sporangia ; he definitely con- 

 siders the 6^. huronensis bodies referable 

 to the water ferns (hence, Protosalvinia) y 

 being misled on the one hand by the fal- 



