Only a few examples in each category are shown below. Goldenrod pollen Solidago canadensis Microorganisms Streptococcus salivarius subsp. Other biological objects Feather Grackel feather in detail. Oat straw is hollow and contains air cells. Nonbiological objects Rust on iron is in the form of tubular efflorescences Deposit on car air filter consists of minute particles covering and clogging the filter.
Evening primrose is a medicinal plant.