Vaccinium macrocarpon Aiton – fruit – SRM 3281*

A temporary water mount was prepared by mixing the dry powder with water and waiting until the material was fully hydrated.

SRM 3281 is a fine powder with some tendency to clump; it is a vivid reddish pink with a slight bluish overtone. Under magnification, most debris consists of either subcellular or multicellular fragments of clear thin-walled cells. Some thin-walled cells found in clusters are irregularly polygonal in shape, 12–27(–40) µm in diameter. Others are elongated rectangular cells, typically 6–21 µm broad, usually broken. Much of the subcellular debris consists of thin-walled, clear fragments of a narrow, irregularly angular shape, usually less than 75 µm long. Subcellular debris also includes a few irregularly rounded reddish inclusions 9–25 µm long and needle-shaped fragments 15–45 µm long. Rare fragments of xylem with helical thickenings, about 6–9 µm in diameter, may be found. There are two major types of pigmented multicellular fragments derived from the fruit wall and seed coat. The more common type has deeply red-pigmented rounded-polygonal to rounded-rectangular cells, usually 18–36 µm in diameter or length, often bordered by similar-appearing cells without pigmentation. The cell walls separating these pigmented cells are entirely clear and relatively thick (3–8 µm, rarely as little as 1 µm). The second type consists of seed coat fragments, whose large, irregularly prism-shaped cells (to over 300 µm long) are only slightly pigmented and bear numerous short striations on the external surface; the cell walls are deeply red-pigmented and very thick (4–12 µm, rarely to 15 µm).

*National Institute of Standards and Technology Standard Reference Material 3281.