Studies of Floral Morphology in the Ericales. I. Organography and Vascular Anatomy in the Andromedeae

Abstract

22 spp. of the Andromedeae are described with respect to the organography and vascular anatomy of the flower: Ampelothamnus phyllireifolius, Andromeda glaucophlla, A. polifolia, Cassiope hypnoides, C. lycopodioides, C. mertensiana, C. tetragona, Chamaedaphne calyculata, Enkianthus cernuus, Epigaea repens, Harrimanella stelleriana, Leucothoe axillaris, L. catesbaei, L. racemosa, L. recurva, Lyonia ligustrina, L. mariana, Neopieris nitida, Oxydendrum arboreum, Pieris floribunda, P. japonica, and Xolisma fruticosa. The Andromedeae are pentacyclic (the outer whorl of stamens opposite the petals), pentamerous, sympetalous, hypogynous, and perfect (except for Epigaea). The stamens have introrse anthers and most have appendages (spurs and/or awns) or varying character. The corolla varies from funnel-form through bell-shape to extremely urceolate. The calyx and corolla in many are strongly reflexed at the flower base. The placentation is in general axile but may become parietal at the top of the depressed ovary. The vascular cylinder in the pedicel forms a complete cylinder. It usually broadens in the receptacle and is broken by gaps above the traces to the various organs. The following whorls of traces arise in acropetal order: sepals, petals, petalad, stamens, sepalad stamens, dorsal carpels in the plane of the petals, septal carpels in the plane of the sepals, and the ventral carpels. There are different degrees of non-divergence of these whorls; most frequently the petal and petalad stamen or sepalad stamen and septal carpel traces are common in origin. Traces to a sepal and septal carpel region may be from 1 to 3; they are single to all other organs. The sepal supply is of 4 types: (a) 3 traces arise to supply each sepal, so that a total of 15 gaps occurs in the vascular cylinder; (b) lateral traces of adjacent sepals have a common origin, so that each sepal received 3 traces and 10 gaps are formed; (c) a single trace for each sepal arises and divides immediately into 3[long dash]each sepal receives 3 traces, but only 5 gaps occur; and (d) a single trace to each sepal. The dorsal carpel bundles form the stylar vascular supply; the septal traces fade out without reaching the style; and the ventral carpels supply the placentae and ovules. The latter bundles normally occur in the plane of the locules but in 2 spp. are found in the plane of the septa. A tentative grouping of the spp. studied, based only on the facts of organography and vascular anatomy described, is given. The initial separation is on the basis of sepal supply; additional characters are used to subdivide the groups.