THE MAIN LINES OF PLANT EVOLUTION 



Dicotyledon eae 



Monocotyledoneae 



Angiospermae 



Lycopsida 

 Spheaopsida \ Filicineae \ Gymnospermae 

 PsilotJ ^ 



Bryophy ta 



Psilophy tales 



Chlorophy ta 



Euglen 



Myxomycophy t 



Cyanophy ta 



Ehodophy ta 



Eumycophy ta 



Protozoa 



Viruses? 

 Chemical Evolution? 



ophy ta 



rophy ta 



ophy ta 



Animal Kingdom ? 



Bacteria 

 ( Schizomycophy ta ) 



Figure 43. A Summary of Probable Lines of Plant Evolution. The dotted lines 

 present highly problematical alternatives. ( Redrawn from Fuller and Tippo. ) 



problem of the origins of these lower groups may be, it appears to be 

 quite clear that the land plants arose from the green algae, with the two 

 phyla, Bryophyta and Tracheophyta arising independently. The bryo- 

 Dhytes have become differentiated into three minor groups, the mosses, 

 liverworts, and hornworts, but have not produced any more progressive 

 types of plants. The primitive tracheophytes (psilophytes), on the other 

 hand, having first succeeded in colonizing the land, quickly gave rise to 

 three more subphyla, the Lycopsida, the Sphenopsida, and the Pteropsida. 

 The first two were dominant groups for a time, but were reduced to minor 

 groups about the end of the Paleozoic Era. Tlie pteropsid line was at first 

 represented only by the ferns, but these gave rise to the gymnosperms 



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