today, nor does it imply that they developed in a single 

 continuous series from the lowest to the highest. We have 

 no particular right to suppose that all plants can be traced 

 back to a single ancestor, indeed the evidence is against it. 

 There is no reason why several phyla, or lines of ascent, 

 may not have originated, perhaps simultaneously, from 

 the most primitive form of living protoplasm. The story 

 of the lower aquatic forms certainly indicates this possi- 

 bility. Of these lower phyla some stopped short, some 

 went on, which ones is a matter to be definitely settled. A 

 good instance, though a somewhat special one, to illustrate 

 the fallacy of the assumption of a single line of relation- 

 ship, is found among the fungi, the chlorophylless lower 

 forms. Many ingenious authors have attempted to unite 

 them in a single continuous series, when every evidence 

 we now have points to their having originated at several 

 places from the green plants. Who, indeed, would care 

 to deny that new phyla might be originating today? Any 

 concept of evolution demands such a possibility; organ- 

 isms are more plastic than the average person conceives, 

 even in this age. 



The object of a natural classification is to consider all 

 the many plant forms, to determine by such marks of 

 genetic relationship as we can discover their place in the 

 series, where they have departed from the main stem and 

 in how far they may have had a line of development of 

 their own. Despite what I have said about the lower 

 phyla, it is not improbable that the higher plants can be 

 traced back to some single source, not that it is to be be- 

 lieved for a moment that this ancestor exists today. Liv- 

 ing ferns or mosses are no more to be considered the direct 

 ancestors of the flowering plants than are monkeys to 

 be considered the direct ancestors of man. 



The establishment of our classification today might be 

 compared to the putting together of a puzzle map some 



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