GENERAL PHYLOGENY 



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suppose that the laws which govern the branching of a. limb, 

 which give rise to all the varying forms of arrested development, 

 and which thereby determine a particular modification of the 

 figure which would otherwise result from unmodified growth, 

 must be equally applicable to the general evolution of the higher 

 forms of plants from a common ancestral type. In endeavor- 

 ing to secure a natural growth which would best express all the 



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FIG. 46. Curves for sequence of genera and frequency of anatomical characters 

 of the Cordaitales, Gingkoales, and Coniferales : A, sequence of genera; 

 B, specific characters ; C, generic characters 



conditions involved, the branching system of the Norway maple 

 (Acer platanoides) seems best suited to an illustration of all these 

 phases of terminal growth, suppression, and relations of successive 

 members which we conceive to be represented in the development 

 of plant phyla, inasmuch as it conveys the idea of succession 

 through lateral members in such a way as to indicate the chief 

 line of descent. The branch of the Norway maple, when of vigor- 

 ous growth, is a monopodium, and it is obvious that such would 



