58 



THE THEORY OF EVOLUTION 



of their foliage, had been regarded as true ferns, have 

 had their systematic classification entirely upset. It 

 was found, for instance, that a number of isolated seeds 

 could, with a probability bordering on certainty, be 

 associated with ' fern ' leaves and ' fern ' stems. 1 



Oliver and Scott 

 particularly and 

 Stur previously have 

 done meritorious 

 service in the deter- 

 mination of this 

 most important dis- 

 covery. 



Figs. 16 and 17 

 show a ' fern ' stem 

 and the seed belong- 

 ing thereto, which 

 in exterior form 

 resembles a hazel nut. The new group of these 

 Carboniferous Gymnosperms received the provisional 

 names of ' Pteridospermen/ i.e. seed-plants with fern- 

 like foliage. They are not intermediate forms since 

 there are to-day Gymnosperms with fern-like leaves, 

 e.g. the sago or fern palms. 



We observe then, in the history of the plant world, 

 that with the progress of palaeontology the systematic 



1 Compare with this the instructive statement by F. W. Oliver : Ueber 

 die neuentdeckten Samen der Steinkohlenform, in the Biol. Zentralblatt, 1905, 

 p. 401; Lotsy: Vortrdge uber Bot. Stammesg., II, p. 706; Potonie, in 

 the collected work, Die Natilrlichen Pflanzenfamilien-, published by Engler 

 and Prantl : I, Part iv, p. 780. 



FJO. 17. The seed (L. Oldhamianum, Fig. 16) is 

 enclosed in a husk which is covered with 

 glands. (After Biol Zentralblatt.) 



