Ovular Vasculature in Araceae

Abstract

The pattern of ovular vasculature in Araceae was examined in a broad survey, encompassing 97 genera and over 280 species. Ovular vasculature in most Araceae is limited to a single, unbranched bundle in the funiculus and chalaza and, in the remaining genera, either multiple simple or branched bundles in the chalaza. Integumentary bundles are virtually absent, occurring only in the most proximal regions of the integument of a few genera. The most extensive vascular systems occur in Arophyteae, Peltandra, Typhonodorum, Alocasia, and many Areae. The three-dimensional organization of chalazal vasculature is closely correlated with the orientation of the ovule. In orthotropous ovules, chalazal bundles are generally radially symmetrical. In anatropous ovules, fewer bundles occur on the ventral side of the chalaza than on the dorsal side. Genera with large, orthotropous ovules tend to have chalazal branching more frequently than anatropous ovules. Unusual vascular patterns occur in the temperate genera Orontium and Lysichiton, which are isolated in other characters as well. The systematic distribution of various patterns of ovular vasculature for two new schemes of aroid classification is compared.