Sclereids are specialized cells formed in a variety of shapes.

They have lignified secondary cell walls and are non-living at maturity.

Their primary function is for mechanical support and protection.

photo of sclereid cells

Several of the different sclereid types include:

  • Brachysclereids
  • Macrosclereids
  • Osteosclereids
  • Astrosclereids
  • Trichosclereids

Photo showing brachysclereids in a purple coneflower seed.

Brachysclereids in purple coneflower seed.

Brachysclereids resemble parenchyma cells in shape, but are made almost entirely of secondary cell wall.

These non-living cells are also called stone cells because they form the "grit" in pear fruit.

The inner portion of a sclereid cell is called the Lumen. The lumen is an empty space in the center of a non-living cell bounded by secondary cell walls.

Photo of brachysclereids with lumen and pits pointed out.

Macrosclereids are elongated sclereids usually found in the outer layer in the seed coat of legume seeds.

These cells are responsible for restricting water uptake by hard-seeded legumes.

They are also called Malphigian cells after the pioneering Italian 17th century plant anatomist.

Cross section photo of seed cellular material pointing out the macrosclereids in the seed coat of an eastern redbud (Cercis).

Seed coat in eastern redbud (Cercis).

If the seed coat is macerated with appropriate chemicals, you can see the isolated shape of a macrosclereid.

Photo showing the seed coat of an eastern redbud (Cercis) pointing out the macrosclereids in the shell, with a sepparate photo showing the isolated macrosclereid.

The light line is a continuous line just beneath the outer surface of the macrosclereids in some legume seed coats.

It is actually, an optical refraction of light due to the properties of the macrosclereid.

It was once thought to be responsible for making these cells impermeable to water, but this is probably not the case.

Photo of a seed showing the light line in relation to the macrosclereids of a seed.

Seed coat in eastern redbud (Cercis).

Electron micrograph of the seed coat in honeylocust (Gleditsia).

Electron micrograph of the seed coat in honeylocust (Gleditsia).

Osterosclereids (also called bone or hour-glass cells) are columnar cells similar to macrosclereids except they are enlarged at the ends making them bone-shaped.

Photo of osterosclereids.

Photo of osterosclereids within a mascerated pea seed coat.

Macerated pea seed coats show groups of osteosclereids. In side view, you see the typical "bone shape"

Astrosclereids are branched, pointed, irregular (often star - shaped) sclereids. Astrosclereids are not a common type of sclereid.

They can be found in specialized tissues like the floating leaves of water lily.

Photo showing a example of an astrosclereid with a close up photo to show detail.

Trichosclereids are uncommon cells. They can be found in the leaves of olive and the aerial roots of the Swiss cheese plant (Monstera sp.).

These long trichosclereids are from macerated roots of the Swiss cheese plant.

Photo showing trichosclereids of the Swiss cheese plant.