Identification key for the Hydrangeaceae of California.
Preston, Robert E. and Charles F. Quibell. 2012. Hydrangeaceae in The Jepson Manual: Vascular Plants of California, Second Edition. B. G. Baldwin, D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, and D. H. Wilken, Eds. University of California Press. Berkeley, CA.
Keys and treatments are provided online through the Jepson eFlora:
http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?key=155 (Link to identification key and taxonomic treatments for the Hydrangeaceae of California, including Whipplea.)
http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=48534 (Link to the taxonomic description for Whipplea modesta, including maps of its distribution and specimen collection records).
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