308 



A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



Class IV. Lycopodiales 



1. Eligulatae 



Lycopodiaceae 

 Psilotaceae 



2. Ligulatae 



Selaginellaceae 



Lepidodendraceae 



Bothrodendraceae 



Sigilariaceae 



Pleuromeiaceae 



Isoetaceae 



SUPPLEMENT ON CYCADOFILICES 



With the turn of the century, in addition to those continued trends of work 

 on the various topics which have already been traced, by far the most important 

 contributions to understanding of the Pteridophyta have come from the further 

 discoveries in fossil botany. Interest in this was very greatly increased by sev- 

 eral publications which appeared at this time and were intended for the general 

 botanical reader rather than a geologist or specialist. Renault's Cours de Bo- 

 tanique Fossil e (1881-1886) was one of the earliest, closely followed by Solms- 

 Laubach's Einleitung in die Palciophytologie von hotanischen Standpunkt aus 

 (1887; Eng. trans., 1891). Then in 1899 we have the first volume of Seward's 

 Fossil Plants, and in 1900 Zeiller's Elements de PaUohotanique and the first edi- 

 tion of Scott's Studies in Fossil Botany. 



Comparison of the contents of the three editions of Scott's Studies (1st ed., 

 1900, 2d ed., 1908, 3d ed., 1920) will show the nature of the developments in 

 fossil botany in the first quarter of the twentieth centurj^ More recent infor- 

 mation will be found in Hirmer (1927), Darrah (1939), Walton (1940), Halle 

 (1940), Emberger (1944), Arnold (1947), and doubtless elsewhere. 



One of the most important events of the early twentieth century was the dis- 

 covery by Oliver (see Oliver and Scott, 1905) of evidence for the seed of Lygino- 

 dendron. This was rapidly followed by Kidston's account of fertile structures 

 of Neuropteris and further publications by Scott and Oliver, which are sum- 

 marized in detail in the second edition of Scott's Studies (1908). These dis- 

 coveries remove the Cyeadofilices out of the Pteridophyta and into the gymno- 

 sperms, where they still are under the general name of pteridosperms. A full 

 account of the establishment and subsequent fate of the pteridosperms will 

 doubtless have been included in the paper on gymnosperms and need not be 

 repeated here. They are, however, of importance to the present group because 

 they are the cause of a popular fallacy which has proved very hard to dispel and 

 which, unconsciously, is still liable to affect botanical thought and teaching, 

 the fallacy, namely, that the coal-measure period was an age of ferns. We now 

 know that tlie true ferns were only present in the coal measures in small and 

 archaic forms (the Coenopteridales) very unlike living ferns and that probably 

 all the conspicuous fernlike leaves of that era belonged to seed plants. 



Of greater importance even than the removal of the pteridosperms was the 

 advent of the Psilophytales. The first two of these primitive land plants had 

 been discovered and named by Dawson at a very early date (1859 for Psilophy- 

 ton and 1871 for Arthrostigma) in Middle and Lower Devonian rocks from the 

 Gaspe Peninsula in eastern Canada, but, though known to geologists and to 

 some botanists, they were too unfamiliar in type to be assimilated into the sys- 

 tem for nearly fifty years. Attention was, however, arrested, even during the 



