CHAPTEE III 



RECENT ADVANCES IN OUR KNOWLEDGE 

 OF THE MORPHOLOGY AND ANATOMY OF 

 MEMBERS OF THE PSILOPHYTON FLORA 



IT has been known since the days of Hugh Miller that in the 

 Old Red Sandstone of Scotland a number of simple if somewhat 

 obscure plant remains are to be found. A similar flora was first 

 described by the late Sir William Dawson, from the Lower 

 Devonian of Canada in 1859. Halle 1 has recently pointed out 

 that these are "the remains of the very oldest land-flora at 

 present known ; and it may be stated at once that there is a far 

 greater difference between this flora and that of the Upper 

 Devonian than between the latter and the Lower Carboniferous." 



These fossils, occurring as impressions with only slight traces 

 of their original anatomical structure, have until recently been 

 generally regarded as very doubtful objects and much scepticism 

 has been expressed by botanists as to the morphological inter- 

 pretation of the Scottish and Canadian plants given by Dawson, 

 Penhallow and others. As we now know, this scepticism has 

 been largely misplaced. Except in the matter of affinities, on 

 which point the evidence hitherto has always been very slender, 

 the earlier accounts of these fossils were extremely accurate. 

 The fact that these plant remains are apparently of a simple 

 type of habit has often been explained by an appeal, to the 

 imperfection of the record. Such fossils were commonly regarded 

 as mere petioles or rachises of fronds which had been so damaged 

 before preservation that no 'trace of the lamina now exists. 



It is now, however, quite clear that this conception is funda- 

 mentally erroneous. We know now, in several cases, what was 

 practically the whole of the plant body, and it is clear that 

 instead of dealing with fragments of Cormophytes, as was 

 formerly supposed, we are in reality confronted with a vegetation 

 occupying a lower place in the scale of plant evolution. 



In order to make these matters clear, we propose in the present 

 1 Halle (1916), p. 4. 



