ESSEX BOTANY AND MYCOLOGY GROUPS
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ESSEX BOTANY AND MYCOLOGY GROUPS |
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Dryopteris affinis agg.
Scroll down for records of the segregates.
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___________________________________________________________________________________ Dryopteris affinis agg. Scaly Male Ferns ___________________________________________________________________________________ This taxon is a 'mess' of complex hybrids that reproduce apogamously and is currently spit up into three taxa at specific, as opposed to their former status, at subspecific level. Dryopteris borreri is the most frequent in Essex, probably with hundreds of sites; D. affinis (formerly D. affinis subsp. affinis) is apparently very rare, but probably overlooked, although once known it is very distinctive. Dryopteris cambrensis has been found in Hertfordshire so it could well turn up in Essex. Descriptions in the books are often contradictory so it’s best to stick to a few definitive features. All three are unable to reproduce sexually, the prothalli producing antheridia (which can fertilize D. filix-mas to produce hybrids) but not archegonia, new sporophytes arising directly from prothallial tissue which then produce spores that develop into prothalli that repeat the cycle. This apomictic mode of reproduction means that any mutations accumulate so that colonies in a given area may form recognizable morphological clones. To complicate matters further, D. affinis sensu stricto has now been formally split into three subspecies: affinis [thus reinstating subsp. affinis but in a much more strict context]; of the other two, it appears that subsp. paleaceolobata is being found to extend increasingly eastwards and we should therefore look out for it. All three of the following can form hybrids with D.filix-mas, and the first generation hybrids have been given formal names [see below appended to each species account] but these can then back-cross to form a further series of secondary hybrids which have not been given formal names! See Stace III p.33-37 for more details. D. borreri is usually of much the same stature, colour and surface texture as D. filix-mas, but like the other D. affinis s.l. segregates, it has a dark (grey/purplish) spot on the underside where each pinna joins the rhachis; it also has noticeably parallel-sided pinnae and pinnules, the latter being truncate at their ends. It has more golden scales on the lower rhachis than D. filix-mas, but less so than D. affinis. Unlike the next, its fronds die back in the autumn. D. affinis is a much larger plant with leathery, dark green, glossy fronds that tend to be more upright, and stay green through most winters.. It too has the dark spot, and its rhachis is densely smothered in long golden scales. The ends of the pinnules lack the truncate shape of borreri. Our plants so far recorded are all D. affinis subsp. affinis in which the lowest downward facing pinnules of the lowest pinnae are not the longest and are unlobed or scarcely lobed, whereas in subsp. palaeceolobata the corresponding pinnules are longer than the rest with small distinct lobes. Subsp. affinis and susbsp. palaeceolobata have the edges of the indusia covering the sori tucked under the edge of the sori when young, like a kidney-shaped doughnut, as opposed to the edges curving over and then outwards to form a flat flange as in D. filix-mas. D. cambrensis is similar to D. affinis, with the dark spot, shiny leaves and masses of scales on the lower rhachis - but these have a reddish-tinge to the gold. The pinnules get evenly smaller all the way down the pinnae, as opposed to being the same length for at least half-way in the other two, and the pinnules are rounded rather than truncate at the apex, the lowest on each pinna having a substantial basal lobe that overlaps the rhachis. Like D. borreri, its fronds wither at the first frosts. Its inducia shrivel to form a pye-crust shape.
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___________________________________________________________________________________ Dryopteris borreri (Newman) Fraser Jenk. Borrer's Scaly Male Fern ___________________________________________________________________________________ Light 8. Wetness 7. pH 6-9. Fertility 3. Height <80cm Native. Native. This is the most widely distributed and abundant of the three segregates in Britain, and has the greatest range of habitat tolerance, ranging from mortared walls to the acidic soils of pine plantations (C.N.Page 2007). In Essex we only seem to find it as scattered individuals in slightly acidic habitats. Its fronds usually unfurl about a week later than those of D. filix-mas at any given site, but unlike D. affinis s.s. they die back in the autumn. Once one has an eye in for it its truncate pinnules give it a distinctive giz, although hybrids with D. filix-mas can complicate identification. Furthermore not all plants included in the circumscription have the truncate apex to the pinnules, but the dark mark at the junction with the rachis is diagnostic in combination with an indusium that shivels to a 'chanterelle' rather than with permanently tucked under edges as in D. affinis s.s. It usually grows with D. filix-mas but seems to require rather more moisture. The F1 hybrid with D. filix-mas is known as D. x critica. All records: |
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