Tubular filaments of fungi called hyphae may also be seen in a direct smear. Hyphae stain Gram positive and may branch or intertwine. Parasites can also be identified with the Gram stain, although it is not as sensitive as the special stains used for parasites. The Gram stain reaction and appearance can be used to identify most cellular material seen in a direct smear. The crystal violet may precipitate and can be seen on the slide. If the stain has precipitated, it must be refiltered before use.