Vascular Patterns in Stems of Araceae: Subfamilies Calloideae and Lasioideae

Abstract

The stem vasculature of representative species in the four genera in the Calloideae and eight of the 17 genera in the Lasioideae was analyzed with films of series of cross sections, a technique only suitable for taxa with distinct internodes. The Calloideae are characterized by axial bundles which are more or less amphivasal and have an irregularly anastomosing vascular interconnection. The bud-trace system is short, inconspicuous, and has a narrow insertion. In the Lasioideae the climbing genera Cercestis and Rhektophyllum are most like each other but are both different from other members of the subfamily; the resemblance of Cercestis to Culcasia (Pothoideae) is recalled. Montrichardia is distinctive because of its elaborate compound-stem vascular bundles. This compound condition can be distinguished from the superficially similar arrangement found in some other taxa, e.g, Lasia, Cercestis spp, and Rhektophyllum, where there is an arrangement intermediate between simple and compound bundles. Here leaf traces and axial bundles retain their identity for some distance after association, but their vascular tissues eventually become continuous. Four distinct types of bud-trace insertion are recognized. Some comparison is possible with other subfamilies (Pothoideae, Monsteroideae) which have been examined so far in this survey.