ABSTRACT
Vascular plants that grow in vernal pools are receiving attention and study as they become rarer due to continued destruction of their unique habitat. Vernal pools are not restricted to California, but in North America they are found mainly in this state. This chapter presents the details of a study conducted in the northern Sacramento Valley was conceived in the spring of 1982 after finding a population of Sidalcea hirsuta. Data presented for Sidalcea hirsuta show that a hundred-fold difference in total seed crop is possible within a period of three growing seasons. Such seed crop fluctuation, in S. hirsuta, is based on plasticity in several responses of the plants. Seeds per fruit can vary significantly from year to year as can fruits per plant, in an even more dramatic fashion. Finally, as would be expected, number of fruiting individuals influences seed crop size.
