As soon as the material is thoroughly washed in water, arrange it so that the filaments will all have the same general direction. This will enable you to get longitudinal and transverse sections. As you begin with the alcohols, use a Petri dish and lay a slide over the material, and keep it .there until you imbed in paraffin. This will keep the filaments from spreading out too much, and you will be able to get as much on one slide as you would be likely to get on a dozen slides without such precaution. Tolypothrix.-This form occurs as small tufts, either floating in stagnant water or attached to plants and stones.
Some species grow upon damp ground.
Like all small filamentous algae, it may be dried on mica for herbarium purposes. Venetian turpentine mounts and paraffin sections are prepared as in Oscillatoria, Tolypothrix is even better than Oscillatoria for a study of the nucleus. Scytonema is a similar form which is fairly common. It is often found as a feltlike covering on wet rocks. In staining forms like Tolypothrix and Scytonema, which have a thick sheath, take care not to obscure the cell contents by staining the sheath too deeply.