The name Oxalis oregana Nutt. is universally accepted for Redwood Sorrel despite a long history of attempted revisions. One of its many current synonyms, O. smalliana R.Knuth, was proposed over a century ago to describe a primarily Californian wood sorrel species distinguishable from the O. oregana type by flower size and color, but recognition of the taxon faded over time. The present study, however, provides substantial genetic, morphological, and phenological support for the reinstatement of O. smalliana as a separate species. A range-wide genetic study of 16 Redwood Sorrel populations showed divergence of two overlapping lineages at both nuclear (internal transcribed spacer) and chloroplast (psbJ-petA) loci. The southern lineage (ranging from Monterey County, California to Curry County, Oregon) corresponds in distribution and floral characteristics to previous descriptions of O. smalliana. The northern lineage, corresponding to O. oregana, ranges from southern Humboldt County, California to southwestern British Columbia. All O. smalliana specimens were characterized by apparent chloroplast heteroplasmy as evidenced by mixed sequence haplotypes, whereas all O. oregana specimens showed typical single sequence haplotypes. Flower size is generally larger in O. smalliana, and its flowers range in color from white to pink, purple, or blue, whereas O. oregana flowers are only white. Analysis of flower color distribution using more than 1000 images identified as O. oregana in the iNaturalist database showed a transition from southern pigmented flowers to northern white flowers in the Klamath Range of northwestern California and southwestern Oregon that correlated with the transition of the O. smalliana to O. oregana genetic lineages. In two sympatric populations, the white-flowered O. oregana was shown to attain peak flowering a full month later than the purple-flowered morph of O. smalliana. Phylogenetic analysis of internal transcribed spacer sequences showed species-level divergence of O. smalliana relative to O. oregana and other members of Oxalis subsect. Oxalis. Median-joining network analysis of haplotype sequences from all taxa in subsection Oxalis was confounded by probable hybridization and introgression, but provided some evolutionary insights. Divergence of the two species is discussed relative to the Pacific Northwest post-glacial north–south recolonization hypothesis.

The amphitropical Trifolium depauperatum Desv. species complex (Fabaceae) is a group of closely related clovers with a disjunct native distribution in Chile and western North America. Based on the most recent treatment by Vincent and Isely in 2012, the species complex includes two species, one of which contains three varieties. Historically, the taxonomy of this species complex has been unstable; therefore, we performed a morphological and molecular analysis from herbarium specimens and fresh tissue to further explore taxonomic delimitations. Multivariate and cluster analyses were performed on the morphological data. Bayesian and Maximum Parsimony phylogenetic analyses were performed on the molecular data. Both data sets support the recognition of four taxa: T. depauperatum var. depauperatum, T. depauperatum var. amplectens (Torr. & A.Gray) Rattan, T. depauperatum var. truncatum (Greene) J.S.Martin ex Isely, and T. hydrophilum Greene. We designate three new lectotypes and one epitype, and provide a key to taxa, synonymy, descriptions, and distributional information for each.

Phacelia damnationensis Kierstead et al. (Hydrophyllaceae) is described as a new species from northern California. The new taxon is a large, perennial, multi-stemmed, generally upright, leafy plant growing from a branched woody caudex. Morphologically it appears most closely related to Phacelia Juss. sect. Baretiana Walden & R.Patt., which contains three other species: P. bolanderi A.Gray, P. hydrophylloides Torr. ex A.Gray, and P. procera A.Gray. This new species is currently known from five general areas in the eastern Klamath Ranges of Shasta County, where it occurs on disturbed open, rocky slopes in conifer forest habitat. We describe the morphological and habitat characteristics for P. damnationensis, another in a series of recently discovered vascular plant taxa endemic to the eastern Klamath Ranges and include an updated species key to Phacelia sect. Baretiana.

Philonotis breutelioides Shevock & Aguero is described as a new endemic moss species restricted to montane and subalpine fen habitats in California from the southern Cascades and Klamath Range south to the southern Sierra Nevada. Molecular data suggests an affinity within the genus Philonotis even though this new species shares morphological character states more frequently observed in the genus Breutelia. Available molecular data suggest distinctiveness of the new species within Philonotis fontana lineage, but they are insufficient to resolve relationships among the taxa in this lineage. Morphologically, Philonotis breutelioides differs from P. fontana by having more narrowly tapered leaves with slightly flexuose apices, leaf base with obvious plications, and elongate thin-walled cells in more numerous rows between costa and margin.