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NZ Plants
Fertile and sterile fronds
In some ferns sporangia are restricted to special fronds with a distinctive form while in other ferns sporangia are restricted to special leaflets in a specific location.
Fertile and sterile fronds of different form on the same plant
During every growing season, some adult ferns form:
- sterile fronds that lack sporangia
- fertile fronds that bear sporangia
The two types of fronds often differ in appearance, a condition known as frond dimorphism (di, two; morph, form). Frond dimorphism is found in many genera of New Zealand ferns.
Blechnum procerum- A plant with prostrate sterile fronds and erect fertile fronds.
Blechnum procerum- Fertile frond (left) and sterile frond (right)
Fertile and sterile leaflets of different form on the same plant
In some ferns all the fronds have a similar appearance but only some pinnae are fertile, eg. the sporangia are restricted to specific locations on the frond.
Todea barbara - Basal portion of a frond, upper surface. Only the basal pairs of secondary leaflets bear sporangia. These often differ in size from the adjacent sterile leaflets.
Todea barbara - Basal portion of a frond, lower surface. Sporangia are resricted to the fertile secondary leaflets.
