1053. The temperature required to germinate seeds varies from 32ï¾¦ to 80ï¾¦ or 90ï¾¦ ; and some seeds, as those of the Australian acacias, may be immersed in water at the boiling point without destroying vitality. The seeds of no plant will vegetate under 32ï¾¦, because below that degree water freezes, and consequently could not be absorbed by the tissue of the seed. The common annual grass (Poa annua) will vegetate at, or very slightly above, that temperature, as will the chickweed (Alsine media), the common day nettle (Lamium rubrum), and various others. The seeds of wheat, barley, rye, and beans, have preserved their vitality at a temperature low enough to freeze mercury.