The cilia of the large spermatogoid of Ginkgo and the cycads stain beautifully in iron-alum haematoxylin, which not only stains the cilia but even differentiates the free portion from the part between the blepharoplast and the surface.
The cilia of sperms of Bryophytes and Pteridophytes stain better with gentian-violet or crystal-violet. The periods are long; not less than 30 minutes, and often several hours will be required.
The cilia of the motile spores of Thallophytes may often be demonstrated by allowing a drop of the iodine solution used in testing for starch to run under the cover.
Zimmermann gives the following method: Bring the objects into a drop of water on the slide and invert the drop over the fumes of 1 per cent osmic acid for 5 minutes. Allow the drop to dry. Then add a drop of 20 per cent aqueous solution of tannin, and after 5 minutes wash it off with water. Stain in a strong aqueous solution of fuchsin (or carbol fuchsin) for 5 minutes. Allow the preparation to dry completely, and then add a drop of balsam and a cover. The cilia should take a bright red.
Zimmermann also found the following method satisfactory for the cilia of the zoospores of algae and fungi: Fix by adding a few drops of 1 per cent osmic acid to the water containing the zoospores; then add an equal amount of a mixture of fuchsin and methyl violet. The fuchsin and methyl violet should be 1 per cent solutions in 95 per cent alcohol. In a few seconds the cilia stain a bright red.
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