Frond dimorphism refers to a difference in fern

Fern

A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

s between the fertile and sterile frond

Frond

The term frond refers to a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group...

s. Since ferns, unlike flowering plants, bear spore

Spore

In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

s on the leaf

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 blade itself, this may affect the form of the frond itself. In some species of ferns, there is virtually no difference between the fertile and sterile fronds, such as in the genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Dryopteris

Dryopteris

Dryopteris , commonly called wood ferns, male ferns, and buckler ferns, is a genus of about 250 species of ferns with distribution in the temperate Northern Hemisphere, with the highest species diversity in eastern Asia. Many of the species have stout, slowly creeping rootstocks that form a crown,...

, other than the mere presence of the sori, or fruit-dots, on the back of the fronds. Some other species, such as Polystichum acrostichoides

Polystichum acrostichoides

Polystichum acrostichoides is an evergreen fern native to eastern North America from Nova Scotia west to Minnesota and south to Florida and eastern Texas...

(Christmas fern), or some ferns of the genus Osmunda

Osmunda

Osmunda is a genus of primarily temperate-zone ferns of family Osmundaceae. Five to ten species have been listed for this genus.The species have completely dimorphic fronds or pinnae , green photosynthetic sterile fronds, and non-photosynthetic spore-bearing fertile pinnae, with large, naked...

, feature dimorphism on a portion of the frond only. Others, such as some species of Blechnum

Blechnum

Blechnum is a genus of between 150–220 species of ferns in the family Blechnaceae, with a cosmopolitan distribution. By far the greatest species diversity is in tropical regions of the Southern Hemisphere, with only a few species reaching cool temperate latitudes in the Southern Hemisphere...

and Woodwardia

Woodwardia

Woodwardia is a genus of 14-20 species of ferns in the family Blechnaceae, native to warm temperate and subtropical regions of the Northern Hemisphere. They are large ferns, with fronds growing to 50-300 cm long depending on the species.-External links:****Huxley, A., ed. . New RHS Dictionary of...

, have fertile fronds that are markedly taller than the sterile. Still others, such as Osmunda cinnamomea (Cinnamon fern), or plants of the family Onocleaceae

Onocleaceae

Onocleaceae is a small family of terrestrial ferns. There are four genera of onocleoids: Matteuccia, Onoclea, Onocleopsis, and Pentarhizidium, consisting of five species largely in north temperate climes....

, have fertile fronds that are completely different from the sterile.