1. The effect of soaking in water on the subsequent germination of several species of Gramineae has been determined under a variety of conditions.

2. With most species an acceleration of germination results from presoaking, but this may be negligibly small under optimum conditions in the soil.

3. Dryness of soil and a relatively low temperature greatly increase the differentiation between the germination of soaked and untreated seeds. A peculiarly extreme case of such an effect by the second of these factors is provided by Phleum pratense.

4. It is not possible to generalise regarding the behaviour of different species in relation to soaking in water. Closely related species (e.g. Lolium iatalicum and L. perenne, and Festuca pratensis and F. elatior) show considerable differences of behaviour.

5. In none of the species examined is the acceleration produced by soaking so pronounced as is the case in Dactylis glomerata.

6. The acceleration which results from presoaking in Avena sativa is brought about by the start given to the early processes of germination.