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"Didymous roots are those which produce a tubercle each year, and when the tubercle of one year arrives at nearly the dimensions of the one of the preceding year, they answer to the form indicated by the term applied to them; that is, double or twin roots."—Darby, 1855

Didymous Roots

"Didymous roots are those which produce a tubercle each year, and when the tubercle of one year arrives…