Notes on Dryopteris carthusiana

Fig. 1. Dryopteris carthusiana (Vill.) H.P.Fuchs, morph 1 (Finland, Mäntsälä, Ohkola, 1994). – Image: Harri Harmaja (scanned from dry specimen). – This plant clearly deviates from the commonly seen representatives of the species in that (i) the shape and colour of the petiole scales are slightly different, (ii) the lowest pinnae are narrower (i.e., their first basiscopic pinnulae are scarcely larger than the second ones), (iii) the lowest pinnae are fertile, (iv) stalked glandular hairs occur sparsely throughout the both surfaces of the lamina, and (v) glands are even present  in the indusia.

Fig. 2. Dryopteris carthusiana, morph 2 (Finland, Lohja, Koski, 1989). – Image: Harri Harmaja (scanned from dried specimen). – A few tufts with fronds of this kind were found in a half-shady terrace of siliceous rock outcrops, together with e.g. Asplenium trichomanes and Silene rupestris. This kind of plants, with reduced lobation and when sori almost at the segment margins, may be caused by some non-genetic factor such as a phytoplasma. I have found this morph in a few localities in southern Finland.

D. carthusiana (Dryopteridaceae) displays variability in several features, such as the size and relative width of the frond lobes, the amount of glandular hairs in various parts of the leaf (mostly very scattered or absent), and some features of the sori (the latter are larger and appear blackish when the number of well-developed sporangia is great). It is noteworthy that D. carthusiana is composed of two chemotypes in Finland (Widén, C.-J. 1969: Chemotaxonomic investigations on Finnish Dryopteris species and related North American taxa. – Ann. Acad. Sci. Fennicae, ser. A IV Biologica 143: 1-19.). The species as currently conceived may actually consist a few cryptic species.