Cover Illustration: Pollen germination and tube growth in the snow buttercup, Ranunculus adoneus, photographed
under fluorescence microscopy. Snow buttercup flowers exhibit heliotropism, the capacity to track the sun's rays over
the course of the day. The adaptive significance of solar tracking in snow buttercups is mediated through the impact
of flower heliotropism on paternal and maternal floral environments. In controlled crosses, pollen from solar-tracking
flowers has higher germination success than pollen from experimentally restrained flowers. Solar tracking in recipient
flowers also enhances pollen germination and increases pollen tube to ovule ratios. See Galen and Stanton: Sunny-
side up: flower heliotropism as a source of parental environmental effects on pollen quality and performance in the
snow buttercup, Ranunculus adoneus (Ranunculaceae), pp. 724-729 in this issue. Photo credit: C. Galen.
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Copyright © 2003 by the Botanical Society of America, Inc.
