﻿CHAPTER X. 



FERN ANCESTRY AND ANGIOSPERM ANALOGIES. 



THE FERN-CYCAD RELATION SUMMARIZED. 



The evidence indicating the descent of the existing cycads from Marattiaceous 

 tree ferns has been accumulated mainly during the past thirty years. From the 

 botanical side the observations of Wanning on the ancient fern-like characters of 

 the sporophytes, and the recent discovery of the spermatozoids of Cycas, quickly 

 following those of Ginkgo, have been of most weight. On the paleontologic side 

 the testimony of anatomical structure and of development has been mainly sup- 

 ported by the discovery of great complexity in cycadaceous forms, with the existence 

 of a great plexus of seed-bearing quasi-ferns and cycadofilices in the Paleozoic typify- 

 ing theoretical transition forms between ferns and cycads, and most directly by the 

 fact that in the Cycadeoideae the microsporophylls bear the unmistakable stamp of 

 a Marattiaceous origin. In fact, from the earlier belief in the Marattiaceous origin 

 of the cycads, many botanists have come to postulate a pteridophytic origin for all 

 the gyrnnosperms, and indeed such an origin begins to appear quite probable for 

 most spermaphytes. 



Putting aside for the moment, however, the more hypothetical features of 

 present theories of seed-plant evolution, and not overlooking the fact that the com- 

 plexity of the plants with cycad-like foliage strongly suggests remote and widely 

 separated origins from primitive ferns, a startling result is reached when to the 

 evidence regarded as virtually proving the descent of the Cycadaceje from ancient 

 Marattiaeeae is added the category of facts indicating the similar origin of the 

 Cycadeoideae, as follows : 



i. General trunk form, fern-like foliar crown, persistent leaf bases, size, branch- 

 ing, prefoliation, and habits of growth. 



2. Large, soft, pulpy medulla as in Cyathea mcdullaris of New Zealand (which 

 furnishes an article of food similar to sago). 



3. Occurrence of mesarch and medullosan bundles so characteristic of cycado- 

 filices. 



4. Direct course of cycadeoidean leaf traces through the cortex. 



5. Occasional occurrence of incompletely concentric cortical bundles which may 

 be regarded as remnants of earlier concentric bundles. 



6. Vestigial hairy ramentum of Dion and other genera, and abundant ramentum 

 of filicinean type in the Cycadeoideae. 



7. Alternate production of fertile and foliage leaves on the main axis (Cycas), 

 as in Blechnum, Struthiopteris, and Botryopteris. 



8. Prefoliation fern-like. 



9. Leaves partially fertile, as in many ferns (Cyras), and presenting bifurcate 

 (Sta?igeria), odontopterid (Otozamites), and netted-veined (Dictyozamites) types. 



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