Floral Anatomy in Gesneriaceae. II. Gesnerioideae

Abstract

Except for the tribe Bellonieae and one species of Gloxinea, nectariferous tissue was found throughout the Gesnerioideae. It may occur in any of three forms: (1) the thickened base of the gynoecial wall, (2) an annular disk, or (3) a segmented disk. The nectariferous tissue is nearly always vascularized, and the varied nature and source of the vascular supply are described. In the Gesnerioideae, with few exceptions, the wall of the gynoecium contains numerous vascular bundles (appearing as a ring in transection) in addition to the usual carpel supply and its branches. This ring is so conspicuous that it might almost be regarded as a character of this subfamily. In most Gesnerioideae, including the Columneeae and the taxa with an inferior ovary, the disk is vascularized from this ring of bundles. The bundles composing the ring originate largely, although not exclusively, from either stamen traces in the receptacle or stamen bundles in the floral tube. A large posterior gland is found in the Columneeae and Solenophoreae, possibly also in Sinningeae, and a single posterior gland, not enlarged, occurs in Kohlerieae. Stages in the evolution of a single posterior gland may have been preserved in living taxa. The disk in the Gesneriaceae, however modified, is an enation and not an alteration of some preexisting cycle of floral parts. Evidence from the vascular anatomy of the mature flower clearly shows that the inferior ovary of the Gesneriaceae is the result of the phylogenetic union of ovary wall and floral tube; the outer portion of the ovary "wall" is appendicular in origin, not receptacular.