Pollen morphology of 18 species (32 specimens) representing all three currently recognized sections of the genus Elsholtzia (Elsholtzieae–Lamiaceae) was investigated in detail using light, scanning electron and transmission electron microscopy. Elsholtzia pollen grains are small to medium in size (P=20–50 μm, E=16–45 μm), mostly prolate‐spheroidal to prolate, and rarely oblate‐spheroidal to subprolate in shape (P/E=0.95–1.46), hexacolpate (the amb more or less circular or ellipsoid) with granular aperture membranes. Three distinct types of sexine ornamentation are observed in Elsholtzia: perforate, rugulose‐bireticulate, and bireticulate. The bireticulate pattern is the most common, showing a wide range of morphological variation among species. The exine thickness varies from 1.2 to 2.5 μm. Among the present palynological data, the variability observed in sexine ornamentation of Elsholtzia could be of systematic significance. Current infrageneric classification of the genus Elsholtzia is partially congruent with pollen morphological data.

A comprehensive study on nutlet morphology on 46 taxa from the tribe Elsholtzieae was conducted using stereomicroscopy, light microscopy and scanning electron microscopy. The objectives were to evaluate the nutlet characteristics in a systematics context and to provide additional evidence for taxon delimitation. The nutlet shape varied from elliptical, widely elliptical, spheroidal and ovate to pyriform. The size ranged from 0.50 to 2.70 mm in length and 0.34 to 2.65 mm in width. The three types of trichomes included simple non‐glandular trichomes (Collinsonia punctata), clavate non‐glandular trichomes (Elsholtzia cephalantha) and peltate glandular trichomes (Mosla grosseserrata and M. chinensis). We also report the presence of a mucilaginous reaction in nine species of the genus Elsholtzia in Elsholtzieae for the first time. Four types (undulate, papillae‐like projection, thorn‐like pattern and reticulate) and three subtypes (reticulate, reticulate‐cellular and supra‐reticulate) of nutlet surface patterns in the mid‐ventral region were recognized in Elsholtzieae based on the differences in cell outline, outer periclinal walls and dentations of the anticlinal walls. These nutlet micromorphological results may serve as a reference for future hypotheses on the classification of the tribe Elsholtzieae.

Elsholtzia byeonsanensis M. Kim. is an endemic species in Korea, and its leaves are distinguished from other taxa of Elsholtzia by the leathery texture. In this study, we first presented the complete chloroplast genome of E. byeonsanensis . The complete chloroplast genome was 150,628 bp, including a large-single copy region (LSC) of 82,738 bp, a small-single copy region (SSC) of 17,492 bp, and a pair of inverted repeat regions (IRs) of 25,199 bp. It contained 112 genes including 78 protein-coding genes, four rRNA, and 30 tRNA genes. The phylogenetic analysis indicated that E. byeonsanensis and E. splendens formed a monophyletic clade and showed a close relationship. The complete chloroplast genome of E. byeonsanensis will provide useful information for phylogenetic and evolutionary studies.

Pimpinella saxifraga L. (Scarlet pimpernel or Burnet saxifrage), a newly introduced species, was found from Baekyakyi oreum (a parasitic cone or cinder cone) in Seogwipo, Jejudo Island. This species is native to Europe and western Asia and is reported as a widely invasive species around the world. Pimpinella saxifraga is distinguished from other related Korean taxa by leaves that are pinnately compound with 3?7 pairs of segments, which vary from simple, ovate, to 2-pinnatisect, with linear lobes. The vernacular name of "Baek-yak-yi-cham-na-mul" was assigned after the name of the cinder cone where it was initially discovered. We provide descriptions of the morphological characters, photographs and a key to allied taxa in Korea. The geographical origin and introduction routes are unknown, but it is highly likely that it was introduced as fodder given its high nutritious value for sheep and cattle or as a medicinal herb. This species invades commonly grasslands and woodlands and prefers dry, well-drained, and calcareous soils. The distribution of this species was analyzed by searching extensively in surrounding Baekyakyi oreum and adjacent cinder cones, but no other populations were observed. It is protected commonly at the edges or inside of the patchy pine forest in the cinder cone from grazing by cattle; given the worldwide invasive nature of this species, special monitoring and management plans should be developed.

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