Seed micromorphology in Dactylorhiza Necker ex Nevski (Orchidaceae) and allied genera

Seeds of 21 taxa of the genera Dactylorhiza (incl. Coeloglossum), Gymnadenia (incl. Nigritella) and Pseudorchis were examined by light microscope and SEM. Qualitative and quantitative characters were analyzed. In Dactylorhiza, the seeds are fusiform, but some populations of D. viridis show clavate seeds. According to the ornamentation of the periclinal walls, 3 types of seeds are recognized in this genus. The considerable variation in the seed coat ornamentation pattern in the taxa belonging to majalis, maculata, and praetermissa groups of the genus Dactylorhiza is congruent with the genetic processes that occurred during the history of this genus. Gymnadenia shows clavate seeds with stout and straight to slightly curved anticlinal walls, although these are straight to wavy in some taxa considered previously as Nigritella. These taxa also show low values of seed length. Pseudorchis has fusiform seeds without ornamentation in the periclinal walls and fine anticlinal walls. Our study supports the inclusion of the former genus Coeloglossum in Dactylorhiza.