Oak origins From acorns to species and the tree of life

Hipp (Field Guide to Wisconsin Sedges), herbarium director at the Morton Arboretum in Illinois, serves up a stimulating exploration of oak tree biology. Explaining oak reproduction, Hipp describes how male flowers grow organs called stamens that release pollen capable of traveling as far as a football field before, ideally, landing on a female oak flower, where the pollen then produces a "tube" that penetrates the flower's stigma and deposits sperm cells that fertilize the flower's ovule, producing an acorn. Hipp discusses various oak species' surprisingly active survival strategies, noting that, for instance, the Holm oak deals with stress by sprouting "fine roots that are better able to gather resources from the soil." Chronicling the evolution of oaks, Hipp traces the emergence of flowering plants over 100 million years ago, the first acorn's appearance 60 million years ago, and the oak's entrance onto the scene during a period of intense global warming caused by volcanic activity 50 million years ago. Hipp brings a lyrical sensibility to the botany, comparing the genetic recombination that occurs during oak reproduction to Miles Davis's splicing and remixing snippets of recordings to create his song "Pharaoh's Dance," and Rachel D. Davis's black-and-white watercolors provide dreamlike illustrations of the plants discussed. Nature lovers will get a kick out of this. (Dec.)