The floral morphology and anatomy of one representative of the Parnassioideae and two of the Brexioideae are described, and some of the recent literature dealing with the Saxifragaceae sensu lato is reviewed. Comparison of the floral structure in Parnassia to that typical of the Saxifragoideae, the subfamily constituting the Saxifragaceae sensu stricto and which, therefore, may be considered to show the basic saxifragaceous characteristics, reveals little similarity. Parnassia differs in pattern of both sepal and androecial vascularization, vascularization and degree of connation of the carpels, height in the gynoecium to which ventral bundles remain compound, possession of nectariferous staminodia, and the absence of epidermal appendages. Brexia and Ixerba (both of the Brexioideae) are strikingly dissimilar in floral structure and probably should be dissociated. While the position of Ixerba is problematical, it shares more floral characters with the Escallonioideae than with either Brexia or the Saxifragoideae and is better associated with that taxon. In both Parnassia and Brexia the vascular pattern suggests derivation of the androecium from a fascicled condition: the vascular supply of each filament consists of a cylinder of closely associated collateral bundles, and each staminodial set receives a single vascular complex which subsequently divides into as many vascular strands as there are staminodia in the set.

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The floral anatomy and morphology of 26 species from the Saxifragoideae and three from the Iteoideae are described and compared. The flowers of the Saxifragoideae are predominantly actinomorphic, partially epigynous and/or perigynous, and pentamerous, with two carpels which bear numerous ovules. There is usually some degree of independence between carpels, and the normally separate styles possess both a canal and transmitting tissue. Generally, staminodia are absent and nectariferous tissue, which is not vascularized, is present. The subfamily is characterized by large multicellular trichomes with globular, often glandular, heads. Placentation may be parietal, axile, or transitional between the two; parietal appears to be a derived condition in the subfamily. The vascular cylinder in the pedicel generally consists of several to many discrete bundles from which diverge ten compound traces at the base of the receptacle, leaving an inner cylinder of vascular strands that coalesce at a higher level into either as many ventral bundles as carpels or twice that number. In the former case, each ventral bundle consists of one‐half of the vascular supply to each adjacent carpel and separates into individual ventral strands in the distal half of the ovary. The ventral bundles provide vascular traces to the ovules and, along with the dorsals, extend up the style to the stigma. Each trace diverging in a sepal plane typically supplies one or more carpel‐wall bundles, a median sepal bundle, and a stamen bundle. Each petal‐plane trace usually provides one or more carpel‐wall bundles, a lateral trace to each adjacent sepal, a petal bundle and, in flowers with ten stamens, a stamen bundle. Dorsal carpel bundles are usually recognizable and may originate from traces in either perianth plane. While the position of Ribes remains problematical, its floral structure does not easily exclude it from the Saxifragoideae. Floral structure in the Iteoideae is remarkably similar to that in the Saxifragoideae, the main differences being a lesser degree of independence between carpels, generally narrower placentae with somewhat fewer ovules, and the presence of only unicellular, acutely pointed epidermal hairs as opposed to the relatively complex, multicellular trichomes prevalent in the Saxifragoideae.

The floral morphology and anatomy of the one species in the monotypic Kirengeshomoideae, eight species in the Hydrangeoideae, and six in the Escallonioideae are described and compared. Similarities in floral structure and vascularization between Kirengeshoma palmata and members of the Philadelpheae strongly support the placement of this genus in the same subfamily as the tribe—the Hydrangeoideae. While the anatomy and morphology of flowers in the Hydrangeoideae do not clearly exclude the subfamily from a family that also includes the Saxifragoideae, certain commonly appearing floral characteristics probably do. These include relatively extensive polyandry, the frequent occurrence of highly vascularized isomerous gynoecia, petals with lateral bundles originating from traces in the sepal planes, no suggestion of a floral cup continuing beyond the divergence of the floral organs from the carpel walls in epigynous flowers, and essentially no independence among carpels in the ovary region of the gynoecium. In addition, a fascicled stamen arrangement characterizes the polyandrous members (Philadelpheae mostly). Although floral anatomy of too few members of the Escallonioideae has been investigated, the floral characteristics of this subfamily appear to be very diverse and not particularly distinctive when compared with the Saxifragoideae. Some diagnostic trends may be recognized, however: Escallonioids generally have fewer ovules per carpel (except Escallonia), less commonly show independence between carpels, and have epidermal hairs that are quite different from the complex trichomes of the flowers in Saxifragoideae. In addition, the ventral carpel bundles in two species studied in the subfamily terminate at the top of the ovary and do not enter the style.