446 Palaeontologie. 



Pteridospermous seeds, both in Britain and on the Continent, 

 are fuily described and discussed. In concluding a valuable 

 summary of the present position oi our knowiedge with regard 

 to these early seed-bearing plants, the Aulhor states that all 

 the evidence points to the inference that a large part (probably 

 a decided majority) of the fern-like plants of the Carboniferous 

 flora were Spermopkyta, allied most nearly to the Cycadaceae 

 among recent plants, but retaining, in their vegetative striicture, 

 clear indications of affinity with the Ferns. 



The bearing of these conclusions on the question of the 

 evolution of Phanerogams is next discussed. The origin of tlie 

 Cycadaceous Gymnosperms from the Fern stock is now evident, 

 not only from anatomical evidence, but from a knowiedge of 

 the existence of an intermediate group combining fern-like 

 characters with seeds of Cycadean type. At the same time it 

 must be remembered that the ancestors of the Pteridospermeae 

 are still unknown, and may have differed in important respects 

 from Ferns as we understand them. What we are entitled to 

 say on present evidence, is that the most primitive secd-plants 

 known to us present close aftinities with the Ferns, and must 

 have Sprung, with them, from a common stock, while they 

 show no indication of any near relationship to the other families 

 of Pterldophyta. 



The Author next passes to the Cordaiteae, another group 

 of Palaeozoic seed-plants, and brieily traces the growth of our 

 knowiedge of the structure of Cordaites and its seed. With 

 regard to the latter organs he remarks that no great weight 

 can be attached to the difference in symmetry, bilateral in 

 Cordaiteae, radial, so far as we known, in Pteridospermeae, for 

 in the recent Cycadaceae, the seed is bilateral in Cycas, but 

 radially symmetrical as regards interna! structure in all the 

 other genera of the order. 



He concludes that, taking into consideration both the 

 seed-characters and those of the vegetative anatomy, there is 

 every reason to believe that a real affinity existed between the 

 Cordaiteae and the Pteridospermeae. The Cordaiteae are so 

 ancient that their origin lies further back than our records ex- 

 tend. But the evidence distinctly points to the conclusion that 

 at some remote period they sprang from the same stock to 

 which the Carboniferous Pteridospermeae belong, and conse- 

 quently that they too, like the Cycadopliyta, were ultimately 

 derived from Cryptogams allied to the Ferns. Considering, 

 however, the enormous antiquity of the Cordaiteae as compared 

 with the comparatively late appearance of the true Cycadophyta, 

 it seems probable that the two classes originated separately, 

 and at very different periods, from a plexus of primitive, fern- 

 like seed-plants. While certain families within this plexus seem 

 to have made rapid progress, and in the Devonian period had 

 already advanced to the rank of well-characterised Gymnosperms, 

 the remainder long retained much of their primitive fern-like 



