1. The spores of a club moss, with individual structures about 0.03mm in diameter. Easily transported by and almost indestructible in cave water, the spores can be dyed a variety of colors, and offer a valuable water-tracing technique. Preparation and collection of the spores is very tedious, and the method lacks the convenience of using simple dyes . 2. Spores of Lycopodium clavatum, which can be used in natural or dyed color as a label in studying ground-water movement in karst areas .