How do fern sporangia release spores?

The method by which fern sporangia release spores depends on the type of sporangium:

• Leptosporangia: Most common in typical ferns, these structures feature a specialized row of cells called an annulus. As the sporangium dries, the annulus undergoes stress, causing the capsule to open and tear apart. Eventually, the water film within the annular cells breaks, causing the annulus to snap back to its original position, which explosively tosses the spores into the air.1
• Eusporangia: Found in more primitive ferns, these sporangia have thicker, multi-layered walls. They open through a simple separation along a line of dehiscence due to drying stress. Unlike leptosporangia, they lack a specialized mechanism to throw spores, which are instead simply carried away by the wind.1

In many species, these sporangia are grouped into clusters called a sorus, often located on the undersurface of the fronds.23