598 



STRUCTURE AND LIFE HISTORIES 



516. Significance of the Pteridosperms. — The close re- 

 semblance of the pteridosperms to ferns, on the one hand, 

 and to modern cycads on the other, justifies the conclu- 

 sion that they represent a "connecting link" between the 

 true ferns and the cycads, and that the modern cycads 

 have descended from the same ancestry as the modern 

 ferns, each developing along somewhat different lines. 



Fig. 420. — Slangeria paradoxa Moore. Specimen from the cycad 

 house at the New York Botanical Garden, bearing, at the apex of the stem 

 a carpellate cone. (Photo from New York Botanical Garden.) 



It was in recognition of their vegetative resemblances that 

 the Pteridosperms were first called (by Potonie) Cycado- 

 filicales. Van Tieghem tersely described them as "phan- 

 erogams without flowers." 



517. A Modem Fern-like Cycad. — One of the modern 

 cycads {Slangeria paradoxa)^ is of much interest in this 



^ Slangeria paradoxa Moore = Slangeria eriopus (Kunze) Nash. 



