INTRODUCTION 



5. Specific identification, because of its 

 great significance, must be made critically. 

 Emphasis should be placed on the positive 

 evidence of similarity rather than on nega- 

 tive evidence of lack, real or fancied, of 

 features which cannot be examined criti- 

 cally. 



6. Neither spores, leaves, nor any other 

 morphological part of a plant in any stage 

 of its life is here considered to he a 

 species. A species of plant, for the 

 purposes of this synopsis, and regardless 

 of how it may be otherwise defined, is 

 regarded as a group of organisms. Any 

 individual organism of such a group, how- 

 ever, may be identified if any diagnostic 

 structure representing any portion of its 

 life cycle is available. Spores in many 

 instances are probably just as definitive 

 of species as any other organ belonging 

 in a coordinated manner to the life cycle 

 of a particular plant individual. They merit 

 study with other types of ancient plant 

 materials, and all data should be recorded 

 on a common basis of taxonomic equality. 

 Because of their unique adaptation for 

 dispersal and their numerical abundance in 

 many sedimentary deposits, it is expected 

 that spores will eventually becon\e of 

 greater practical significance than many 

 of the larger types of plant fossils that are 

 more commonly noted by the geologist. 



7. Since the purpose of giving a name 

 to a taxonomic group is not to indicate the 

 characters or the history of the group, 

 but is simply a convenience in reference, 

 all names that are taxonomically valid and 

 pertinent to recognized groups should be 

 continued. The authors agree that the 

 hyphenated generic nomenclature, for 

 example, Granulati-s pontes, Laevigato- 

 sporites, Denso-sporites, instituted first by 

 Ibrahim (1933), is in poor form, lacks 

 euphony, and tends to be generally mis- 

 leading. Nevertheless, the status of such 

 names seems reasonably secure in several 

 instances and their continuance is likely to 

 cause less misapprehension than attempts 

 to institute more appropriate nomencla- 

 ture. 



The preceding explanatory paragraphs 

 may serve to clarify some of the policies 

 adopted in this and subsequent reports 

 and explain their consistency with sys- 

 tematic treatment of other types of plant 

 material. 



The earliest proposed name requiring 



consideration is Dawson's Sporangites. 

 This name was first proposed in 1863 and 

 has been used ambiguously and in different 

 senses by many authors. It is here re- 

 garded as a nomen ambiguum and the 

 name Tasmanites is adopted for the most 

 frequently encountered forms that have 

 been commonly assigned to Sporangites. 

 Tasmanites nevertheless is a problematic 

 form, spore-like in many of its character- 

 istics, but actually unassignable to any 

 group of plants now known. All the other 

 genera treated here belong with little doubt 

 to the Cormophyta, and all whose affinity 

 is approximately known belong to the Tra- 

 cheophyte groups, as mentioned in the 

 respective generic discussions. 



Knox (1939, 1941) has suggested that 

 spores of Bryophytes may be present in 

 Carboniferous coals, and some forms 

 that have been described may well belong 

 to this group of plants which at present 

 are very scantly recognized in the Car- 

 boniferous. The fact that no spores of 

 Paleozoic Bryophytes are definitely known 

 (Sporogonites Halle may be an exception) 

 makes any suggested correlation hazard- 

 ous at this time. 



It is important to realize that many 

 specific features of spores of different 

 geologic age can be matched because of 

 evolutionary convergence as well as be- 

 cause of community of derivation. Con- 

 sequently unless there exists some cor- 

 roborative evidence based upon spore 

 forms actually present in contemporane- 

 ous fossils whose relationship can be 

 established, all that seems warranted is to 

 direct attention to similarity of the spores 

 of different geologic age, recognizing that 

 the similarities may or may not have phy- 

 letic implications. 



There is some lack of strict agreement 

 between the morphological nomenclature 

 applied to modern pollen and the morpho- 

 logic features of fossil forms. For one 

 thing the microspore in modern forms is 

 determined, in a strict sense, solely by the 

 presence of the unicellular male gameto- 

 phyte.^ Such a distinction is of course 

 inapplicable to fossil forms. There is also 



2 The common indiscriminate reference to all spores of 

 relatively small dimensions as "microspores" is to be 

 lamented. Although true miscrospores frequently are 

 small, by no means all small spores are microspores. The 

 long established botanical usage of the term "microspore" 

 has reference to fundamentally functional distinctions that 

 are entirely aside from relative or specific size. R. B. 

 Thompson (1927) has in fact demonstrated that in some 

 plants the microspore is larger than the actual megaspore. 



