Features of foliar and stem anatomy of 26 annual and 1 perennial species of North American Agalinis were examined from over 200 population samples. Several species including A. aphylla, A. densiflora, A. filicaulis, A. heterophylla, A. linifolia, A. maritima, and A. oligophylla have distinctive anatomy. Evidence from anatomy supports a reclassification of North American Agalinis at the sectional and subsectional ranks. Agalinis aphylla and A. oligophylla are allied with species of section Erectae, not section Purpureae subsection Setaceae. Agalinis edwardsiana (from section Tenuifoliae) and A. aspera (section Asperae) are most similar to members of section Purpureae subsection Pedunculares. Agalinis tenuifolia (section Tenuifoliae) is similar to species of section Purpureae subsection Purpureae. Anatomical characters range from those usually regarded as xeromorphic to those typical of hydromorphic species. However, different xeromorphic characters are present in species of sections Purpureae, Erectae, and Tenuifoliae. Species of section Purpureae subsection Setaceae have filiform, adaxially grooved leaves; species of section Erectae have narrow, short sclerenchyma-reinforced leaves and very slender stems usually having fiber bundles in their ridges. Species that we retain in section Tenuifoliae have a cylinder of sclerenchyma between the vascular tissues and the fiber-laden cortex. Key words: Agalinis, Scrophulariaceae, anatomy, systematics, taxonomy.
The sequence of events and morphology of structures were similar during early floral development of Agalinis tenuifolia and A. fasciculata. The lateral-posterior calyx primordia were initiated first, followed by the middle-posterior primordium, and lastly by the two anterior primordia. The corolla primordia arose in an anterior to posterior succession, then the four stamen primordia were initiated simultaneously. Later the gynoecium originated as an oval-shaped ridge. Two depressions within it became locules, and the two sides of the cleaved ridge separating them met and formed a septum. A placenta formed in each locule and numerous ovules were initiated on it. Zygomorphy was apparent in the calyx, corolla, and androecium during the primordial stage. Organogenesis in the calyx was rapid so that the calyx lobes and tube were well formed before organogenesis of other floral parts. Except for those of the calyx, floral character states distinctive for each species were manifested late in development of the floral bud.
Initiation of floral primordia begins in Agalinis densiflora with production of two lateral adaxial calyx lobe primordia followed by a midadaxial primordium, and then primordia of two abaxial calyx lobes. Initiation of three abaxial corolla lobe primordia is succeeded by that of two stamen pairs and then by primordia of two adaxial corolla lobes. The primordium of the abaxial carpel appears before the adaxial one. Except for the calyx, initiation of primordia proceeds unidirectionally from the abaxial to the adaxial side of the floral apex. Zygomorphy in the calyx, corolla, and androecium is evident during initiation of primordia and is accentuated during organogenesis. The calyx undergoes comparatively rapid organogenesis, but the inner three floral series undergo a protracted period of organogenesis. The perianth series reach maturation prior to meiosis in the anthers. Maturation of the androecium and gynoecium are postmeiotic events.
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