Many authors use rainfall as sole criterion for deserts.
An additional advantage is given to those species which can survive multiple hydration events if the critical water content is not reached. Those seeds that were 'hydroprimed' germinated earlier and more frequently than those that were not exposed to cycles of hydration and desiccation. Based on characterizations of water stressed environments and principles of physiological ecology, one would expect to see seed coat characteristics that would facilitate the rapid uptake of water. Perhaps most obvious is the advantage expected from seeds with increased surface area to volume ratios . One paper shows such a correlation.