All North American firmosses (Huperzia: Lycopodiaceae) produce highly specialized vegetative propagules known as gemmae. Though gemmae are of interest to morphologists, they have been used only rarely as aids in identification. To improve understanding of their variation among North American species and to explore their systematic utility we surveyed gemmae of all species in North America north of Mexico and provide measurements, comparative descriptions, and images. Several characters of the gemmae, including their size, shape, and morphology of the leaves that comprise them vary considerably across the species studied and can be used to distinguish species. A dichotomous key based on gemma characters is provided, and several notable range expansions are reported. We anticipate this study will help resolve confusion regarding the identity of North American Huperzia species, particularly among the taxa in the northern and western regions of the continent, which remain poorly understood.