28 



PALEOZOIC FOSSIL SPORES 



Haptotypic features. — Lacking or near- 

 ly so. Presumably a weak vestigial imprint 

 of the trilete mark may be present on the 

 proximal cap in some forms as it oc- 

 casionally is in modern Abies. 



Pollen coat. — The unique character of 

 internal bladder wall reticulation distin- 

 guishes these and many other coniferous 

 pollen grains. The internal reticulae add 

 apparent thickness to the perineal blad- 

 der membrane which is quite thin. The 

 exinal (body) wall is much thicker 

 proximally and is least translucent, 

 sometimes appearing brownish under the 

 microscope ; the distal wall is much thin- 

 ner, serving as a harmomegathus and 

 point of germinal exit when ruptured by 

 the expanding gametophyte. 



Affinity. — There can be little question 

 that grains of this sort are referable to 

 the Coniferae. Members of modern 

 Podocarpaceae and Pinaceae show essen- 

 tially similar features. Correlatives of 

 species of Pityosporites represented by 

 vegetative organs are hardly recognized in 

 Paleozoic formations. The presence of 

 such pollen is evidence that such plants 

 existed, possibly as a xerophytic upland 

 flora, and tend to substantiate the view 

 long held that an important ancestry, very 

 scantly represented among megascopic 

 fossils, preceded those highly developed 

 forms found better represented in younger 

 strata. 



Pityosporites represents a group of 

 Coniferae whose pollen is essentially mod- 

 ern in aspect. Florin's brilliant researches 

 (1938-1940) have sufficiently demon- 

 strated that Lebachia, Ernestiodendron, 

 and Walchianthus for the most part do 

 not possess pollen of the Pityosporites 

 type ; most, if not all of the probably 

 correlated but isolated pollen of this sort 

 is referable to Florinites n. gen. described 

 below (p. 56). 



Remarks. — It will be evident that the 

 interpretation given Pityosporites here 

 differs from that of Florin. He (1940, 

 pp. 327-8) considers Pityosporites to be 

 a completely artificial genus which has 

 no type species. Apparently he would 

 assign any pollen-like form with two 

 bladders to this group. It is evident from 

 Seward's descriptions, however (1914, 

 1919, 1933), that the emphasis is not 

 so much merely on the presence of two 

 bladders as it is on the essentially modern 



aspects of these fossils which have been 

 more precisely itemized in our revised 

 definition.' A more restricted group is 

 thus indicated than that considered by 

 Florin, and this group surely is not an 

 artificial one although it certainly exceeds 

 the scope of most "normal" genera, and, 

 in fact, possibly contains elements which 

 would be classed in separate families if 

 more complete characterization could be 

 obtained. Nevertheless, we think it neces- 

 sary to treat the group as a genus at 

 present, with the hope that critical studies 

 later will permit it to be subdivided into 

 somewhat smaller groups that will more 

 perfectly represent the relationships in 

 detail. Whether this hope is a vain one 

 cannot be foretold a priori, but the desira- 

 bility of recognizing a type species for 

 this group which, as we construe it, does 

 signify a definite natural plant alliance, 

 cannot be denied. Part of the taxo- 

 nomist's responsibility is to place the sys- 

 tematic data in order so that later students 

 may revise it to greater perfection in the 

 light of additional data. Such progress 

 is very difficult if nomenclatural types are 

 not definitely indicated and fully utilized 

 in the application of technical nomencla- 

 ture. In paleobotanical studies it is 

 particularly important that this be recog- 

 nized because the nature of the material 

 that is being studied rarely permits cate- 

 gorical statement and new discoveries call 

 for greater revision in preexisting con- 

 cepts, perhaps, than in any other plant 

 science. 



Pityosporites can hardly be considered 

 as synonymous with any modern genus; 

 perhaps the most important reason is that 

 when pollen characters are sufficiently 

 distinctive to permit actual identification 

 with a more precisely delimited modern 

 group, identification with the genus Pityo- 

 sporites becomes inadequate as an ex- 

 pression of affinity. Quite evidently many 

 of the isolated ancient pollen grains can- 

 not be more definitely assigned and Pityo- 

 sporites will serve a most useful function 

 in these instances. 



■^Although Seward (1919, pp. 398-9) has included one 

 of the forms Nathorst reported from the Hor clay as 

 "Pityosporites sp." (which we should prefer to assign 

 to Alisporites) , Seward apparently did this on the as- 

 sumption that Nathorst's specimen was similar to pollen 

 of Picea excelsa. Wodehouse (1935) has shown Picea 

 pollen to be very different. The Pityosporites sp. of Solms 

 from Franz Josef Land (Seward, 1919, p. 399) no doubt 

 is correctly assigned. 



