==The axes are labeled. A-L on the X axis, and I-XIV on the Y. If they appeared without a key, then they’re pretty pictures with no meaning. If, as I strongly suspect, you omitted the key, then you’re intentionally omitting information to claim that it isn’t there.
It’s the only chart Darwin included in his “Origin of Species.” It’s purely a conceptual chart with no actual data points whatsoever. Here are some phrases to give you a flavor of Darwin’s “key.”
“Let A to L represent the species of a genus large in its own country”
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“Let (A) be a common, widely-diffused, and varying species, belonging to a genus large in its own country. The little fan of diverging dotted lines of unequal lengths proceeding from (A), may represent its varying offspring. The variations are supposed to be extremely slight, but of the most diversified nature; they are not supposed all to appear simultaneously, but often after long intervals of time; nor are they all supposed to endure for equal periods.”
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“But I must here remark that I do not suppose that the process ever goes on so regularly as is represented in the diagram”
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“In our diagram the line of succession is broken at regular intervals by small numbered letters marking the successive forms which have become sufficiently distinct to be recorded as varieties. But these breaks are imaginary, and might have been inserted anywhere, after intervals long enough to have allowed the accumulation of a considerable amount of divergent variation.”
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(For some reason, this last passage reminds me of Chauncy Gardner’s explanation of economic cycles in the movie “Being There”—GGG)
“The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth. The green and budding twigs may represent existing species; and those produced during each former year may represent the long succession of extinct species.”