Field Guide to Plant Galls of California and Other Western States, by Ron Russo, UC Press, 2007, 400 pages, $24.95
Many authors would be hard-pressed to write a guide to plant galls that is not also an industrial-strength sleeping aid. But Ron Russo has managed exactly that in this expansion of his 1979 guide: He has created a book that captures the imagination as it educates about a largely ignored field of natural science. Galls are odd and sometimes elaborate structures produced by complex interactions between plant and gall inducer (generally an insect or other arthropod, though fungi and bacteria may also be culpable). These structures—anything from simple swellings to peculiar urchin-like tubercles that plants grow on their leaves or stems—are stimulated by mechanical or chemical signals from the inducing organism and built by the plant host. Far more than instances of simple parasitism, galls can be the foundation of entire eco-systems involving dozens of species.
Russo splits his guide into two sections: a compendium of information about galls and inducers, and well-illustrated “gall accounts” that depict and describe the forms of many galls in the region. The latter is essential for identifying specimens, but the former is where Russo’s experience as a naturalist shines. The descriptions of the give-and-take between plant and inducer are detailed, and the section is packed with interesting nuggets (the treaty ending World War II, for instance, was apparently signed in ink harvested from wasp galls).
Perhaps the most intriguing thing about plant galls is their unexpected ubiquity. Since reading Russo’s guide, I have found and identified half a dozen galls on plants in my own backyard. It is the illumination of the seemingly alien under our noses that makes this guide such a revelation. [David Carroll]