Pteridologische aantekeningen, 4, De bastaarden van het Dryopteris spinulosa-complex in Nederland

Hybrids of the Dryopteris spinulosa complex in the Netherlands Kuntze ex Druce (= D. carthusiana X D. cristata) and D. x deweveri Dryopteris x uliginosa (Joh. Jansen) J. & W. ( = D. carthusiana X D. dilatata) have been recorded from several places in the Netherlands. Fern hybrids, generally speaking, can be recognised by the absence of indurated annulus cells (magnifying glass) and by the presence of abortive spores. Often hybrids tend to show, apart from intermediate characters, monstruosities in leaf shape (especially bifurcations), irregular growth of the crown of leaves sprouting from the rhizome, and hybrid vigour. The diagnostic characters of the hybrids are enumerated. Main characters in D. x uliginosa are: the connection of the basal leaf segments of the 2nd order, which are usually attached with a small part of the blade to a lateral vein; and the presence of a small, dark-centred part at the base of the scale. D. x deweveri can be recognised by scales which are partly pale brown and partly show a darkcentred part (usually not so dark as in D. dilatata). Both hybrids were often found in habitats disturbed by human activities or with considerable environmental changes over short distances. D. x uliginosa was found in habitats with Sphagnum species, D. x deweveri in drained woodlands or in elder carr strongly influenced by birds.