The spores of Equisetum are excellent for illustrating hygroscopic movements. Shake out the spores from the strobili and let them dry thoroughly. They can be kept dry for years. When wanted for demonstration, put a few on a slide, moisten a little, and watch the movements under the microscope. Strobili of other species, like E. fluviatile and E. hiemale, contain a large amount of silica and, consequently, only the younger stages cut well in paraffin.
Hydrofluoric acid damages the cell contents more or less.
In species like these, all stages in the development are found in a single season. The Gametophytes - The spores of Equisetum germinate as soon as they are shed, but, like all spores with a considerable amount of chlorophyll, they do not long retain the power of germination. A comparatively small percentage will germinate a week after shedding, and after a month, there may be no germination at all. There is no difficulty in growing prothallia to maturity and securing stages in the embryo, if fungi or blue-green algae do not appear and ruin the cultures. The prothallia fix well in chromo-acetic acid.