This thesis examines growth-form in the genus Smilacina (Liliaceae) including a detailed morphological study of one species, Smilacina racemosa (L.) Desf., and comparative studies of other species in ...the New World. The perennial rhizome of S. racemosa is a sympodium composed of the persistent basal portions of annual shoots. The upper portion of the shoot forms a discrete abscission zone at its base prior to its senescence. The perennial sympodium develops in a morphologically precise fashion; preformation and periodic growth are fundamental. An analysis of vascular organization in the sympodium that includes techniques of cine photography and vital staining demonstrates the high level of structural and functional integration among constituent sympodial units. Comparative studies of rhizome form are based on a taxonomic monograph of the New World species that includes typification of 80 basionyms, keys, maps of geographic distribution, as well as technical descriptions and illustrations of each species. (Maianthemum Weber. is considered congeneric with Smilacina Desf., but is not included in the study.) Smilacina in the New World consists of two geographically disjunct groups, with centers of taxonomic diversity in eastern Canada and Guatemala. Three species and two subspecies are recognized north of Mexico. Eight species, two of which are new, and six subspecies, two of which are new, are recognized in Central America. The comparative studies of rhizome morphology indicate that trends toward elongated internodes and loss of lateral buds accompany reduction in the inflorescence.
