334 TRANSACTIONS OF SECTION K. 



WEDNESDAY, SEPTEMBER 10. 



The following Papers were read : — 



1. The Relation of the Seed Plants to the Higlier Cryptograms. 

 By D. H. Scott, F.R.S. 



That the Seed Plants sprang from the Higher Cryptogams has been an accepted 

 doctrine ever since evolutiona,ry ideas were first entertained. The discovery of 

 tha Pteridosperms — Fern-like Palfeozoic plants bearing seeds — has led many 

 botanists to believe that the Spermophyta generally, or at least a great part of 

 them, were ultimately derived from the Ferns. Sometimes, however, greater 

 caution has been shown and only a ' common stock ' postulated. Zeiller, always 

 judicious, inclined to the latter hypothesis, but he, too, was much impressed by 

 the Fern-aifinities of the Pteridosperms, which he called ' Fongeres a graines,' 

 seed-bearing Ferns. 



A reconsideration of the question has suggested a doubt whether the 

 Pteridosperms ever were Ferns, and, further, whether the Peed Plants are not 

 as ancient a race as any known phylum of the Higher Cryptogams (leaving the 

 newly-recognised Psilophy tales out of consideration). Though the point at issue 

 affects the position of the Spermophyta as a whole, the question turns on the 

 Pteridosperms, as they are the Seed Plants which bear the most manifest 

 resemblance to a definite Cryptogamic stock. 



The doubt was first raised by Prof. Weiss 's observation that in the roots of 

 Lyginopteris old/iamia the xylem-plate of the diarch rootlet is parallel to the 

 axis of the parent root, as in Thanerogams, not at right angles to it, as in 

 Pteridophyta. This, though a small point, seems to afford, so far as it goes, an 

 absolute distinction, showing that in this respect the typical Pteridosperm, 

 Lyginopteris, was a true Phanerogam.. 



Much stress has always been laid on the anatomical characters of 

 Pteridosperms as evidence of an intermediate position between Cycadophyta and 

 Ferns. It is remarkable, however, that no Pteridosperm is known to resemble 

 in its anatomy any contemporary group of Ferns. We may arbitrarily compare 

 Lyginopteris with Osmnnda or Heterangium with Ghichenia, but these are mere 

 analogies, for no one can imagme that there was any affinity between the genera 

 compared. With Palfeozoic Ferns, whether Primofilices or Marattiales, there 

 seems to be little or nothing in common, from an anatomical point of view. The 

 evidence may indicate a certain parallelism of development, but by no means 

 supports filiation. 



The resemblance in habit between Pteridosperms and Ferns is striking and 

 obvious; it deceived almost all botanists, even Hooker himself, down to our own 

 time. But in some cases, where the external likeneas is great/est {e.g., between 

 Alefhopteris and Pteris), we know that the internal structure was totally 

 different ; habit by itself is an il'lusory guide. 



The seeds of Pteridosperms show no clear relation to Fern-sporangia, from 

 which they are just as remote as those of Cordaitere or even Cycads. This is 

 very different from the case of Lepidocarpon or Miadesmia, where the Lycopod 

 relation is manifest. There is no reason to assume that the Pteridosperm-seed 

 ever was like a Fern-sporangium ; attempts to correlate them have depended on 

 the aid of ingenious hypotheses with little basis of fact. 



The poUen-iSacs of Pteridosperms offer a better analogy with the sporangia 

 of Ferns ; they have generally been regarded as practically identical with the 

 fructifications of Palreozoic Marattiales. We really, however know very little 

 about the microsporangia ; if they were bilocular, as there is some evidence to 

 show, they were very distinct from Fern-sporangia of any sort. 



It is suo-gesterl that the Pteridosperms (and i>x hypothesi the Seed Plants 

 generally) have always been distinct from any of the known phyla of Vascular 

 Cryptogams ; that they were not derived from the Primofilices of Arber or from 

 any other group of Ferns recognised as such. The writer's object is to emphasise 

 the distinctness of the Pteridosperms as an independent phylum, parallel in 

 important respects to the Ferns, but of imknown and remote origin. 



Zeiller thought that in the older Palaeozoic rocks Pteridosperms were more 



