Lycopodium clavatum has erect, leafy stems arising at intervals from horizontal (also leafy) stems spreading along the surface, or beneath fallen leaves, but not beneath the soil. The leaves spread from several sides of the vertical stem, giving a round cross-section to the branches (i.e. the branches are not conspicuously flattened in appearance--see the Dicanthelium species for example of flattened branches). Spores are produced in sporangia located only in specialized "strobili" or cone-like structures at the ends of the leafy vertical stems. L. clavatum is separated from other species in this group by having a narrow elongated stalk between the leafy stem and the strobilus, and by the lack of conspicuous narrowings along the vertical stems, called annular (or annual) constrictions--see L. annotinum for the alternative to both characters. L. clavatum and the similar L. lagopus both have elongate, hairlike tips to each leaf, unlike the leaves of all our other Lycopodium species. The much less common L. lagopus is distinguished by having only one strobilus per vertical stem, versus more than one strobilus per stem for L. clavatum. Another helpful character to help distinguish these two species is the number of lateral branches from each vertical stem. L. lagopus generally has 2 or 3 branches and L. clavatum has 3-6 branches. It is necessary to check these characters for many stems in a population to arrive at a conclusion, since occasional exceptions on a single stem may occur for either character.