As a result of the experiments carried on to determine the effect of moisture upon seed production in alfalfa, the following conclusions have been drawn, based upon the work of the experiments as presented in this bulletin:

1. The setting of seed pods in alfalfa, (Medicago sativa), is dependent upon the proper functioning of the pollen.

2. Germination of the pollen depends upon a proper supply (l! moisture. If the water supply is either above or below a certain requirement, the pollen does not germinate.

3. The water requirement for germination of the pollen depends upon a certain ratio between the moisture delivered by the stigma and the moisture of the air surrounding the stigma.

4. It follows, therefore, that when the optimum supply of soil and atmospheric moisture for pollen germination is available, an increase in soil moisture, resulting in an increased moisture delivery of the stigma, or a change in the atmospheric moisture, disturbs the required moisture supply for pollen germination and prevents fertilization.

5. The blasting of seed is due to the arrested development of the embryo.

6. This arrestment may be due to the plant's inability to furnish the proper water and food supply for the maturing of seed during drought, or it may be due to the pathological condition to which the seed is more susceptible under drought conditions.