Fern Leaf Cross Section Under the Microscope
Fern Leaf (Cross Section), Polypodiopsida
This is a cross section of a fern leaf (frond) stained with safranin. It shows the thin leaf blade and, on the underside, the spore-making structures that ferns use instead of seeds.
This is a cross section of a fern leaf, or frond, stained with safranin. The thin leaf blade has a single layer of epidermis cells on each surface, with loose, spongy mesophyll cells between them that carry out photosynthesis. Small round veins, called vascular bundles, carry water and food along the blade, and a thicker midrib holds the largest ones. On one side, a sorus sticks out from the leaf: a cluster of sporangia (spore cases) under a protective flap called the indusium. Ferns spread by these spores instead of seeds.
What to look for
- Epidermis: Single layers of cells on the upper and lower surfaces of the leaf.
- Mesophyll: Photosynthetic cells between the two surfaces, with air spaces between them.
- Vascular bundle: A vein with thick-walled xylem cells, stained deep red, and phloem around it.
- Sorus: A cluster of spore cases on the underside of the leaf.
- Sporangia: Small rounded spore cases, each with a row of thickened cells (the annulus) that helps fling spores out.
- Indusium: A thin flap that covers and protects the sorus in many ferns.
Questions and answers
What are the brown dots on the underside of a fern leaf?
They are sori, clusters of sporangia (spore cases). Ferns reproduce with spores rather than seeds, and each sporangium releases many tiny spores.
What does a fern sorus look like under a microscope?
In a cross section, a sorus looks like a cluster of small round capsules on stalks attached to the underside of the leaf. Each capsule is a sporangium full of spores, often covered by a thin flap called the indusium.
Compare it
- Category
- Botany & Plants
- Scan magnification
- 20x
- Stain
- Safranin
Viewing this slide in class
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