I learned about Ynes while flipping idly through the 1974 edition of Notable American Women: A Biographical Dictionary (volume II, G-O, incidentally), "prepared under the Auspices of Radcliffe College," as it says on the frontispiece.
By far the most comprehensive thing I read was biography for young readers called Ynes Mexia: Botanist and Adventurer by Durlynn Anema.