Micropyle is the narrow pore or passage left by the integuments at one end of the ovule. It allows the entry of pollen tube into the ovule. This phenomenon is known as porogamy It is most common, e.g., Lily. Germination of pollen grain occurs by absorbing water and nutrients from the stigmatic secretion. Pollen tube is produced which grows downward through the style toward the ovary. It is protected and nourished by the style tissue. Pollen tube could not grow long enough to reach the ovules if it could not absorb nutrients from the style.