2O6 



HEREDITY AND EVOLUTION IN PLANTS 



are found on pinnules of ordinary foliage leaves, resem- 

 bling the sporophylls of certain ferns (Fig. 90) rather than 

 the stamens of modern flowers. 



The discovery of the seed-bearing character of the fern- 

 like plants of the Paleozoic has been called the most im- 

 portant contribution of paleobotany to botany ever made. 

 It was predicted by Wieland, of Yale University, nearly 

 two years before it was announced by Oliver and Scott. 

 It is now believed that seed-bearing plants of the pterido- 



FIG. 90. Top, lateral pinna from a leaf of Marattia fraxinea. (After 

 Bitter.) Below at left, synangium of same. (After Bitter.) At right, 

 cross-section of the synangium. (After Hooker-Baker.) 



sperm type were nearly as numerous in the Paleozoic 

 as were the cryptogams. 



140. Significance of the "Pteridosperms." The close 

 resemblance 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. 



