BPS Guernsey Fern Trip - March 2015
This weekend the British Pteridological Society held a vist to Guernsey to see some of the extraordinary cryptogams on the island, some of which are endemic (more on those later). To keep the post brief I will not go into depth on the less unusual species seen by the group, however I will list them at the end along with their distribution.
Ophioglossum lusitanicum
This is an exceptionally rare fern in the British Isles and quite rare throughout its entire native range. The Guernsey locality at Fort Hommet is a patch around 2x2m. The plant grows amongst moss on thin, peaty and sandy soil. Although exposed to strong winds, the site is protected by a large boulder on the north side and recieves warmth due to its south facing exposure. The plant itself is not particularly conspicious with the sterile fronds measuring 1cm or less in length, underwhelmed is most people's first feeling on seeing it! This year has not been particularly good for seeing fertile fronds, with just one fertile plant in the entire colony. The result of of poor weather and grazing from rabbits.
N49°28'23" W2°36'20"
Isoetes histrix
Another Guernsey rarity, also growing at Fort Hommet. This is the only native land dwelling quillwort species and it seems to be quite picky in terms of habitat; generally found growing around coastal turf in bare peaty soil which is often seasonally flooded.
At first, identification seems like a daunting task as Isoetes histrix tends to grow in the same habitat as all of its angiosperm dopplgangers! Scilla autumnalis can be dismissed immediately as it is far less foliaceous and the few leaves it does have are long and strappy in contrast to the numerous short leaves of Isoetes. Other possible confusion can be avoided by observing the distinctive white lines of stomata down each side of the leaf in Isoetes; this feature being absent in all other possible sources of confusion.
N49º 28'29" W2º 36'25"
Anogramma leptophylla
This is a very special species as it is the one of the only ferns with an annual sporophyte stage. It is exceptionally rare in the British Isles, the Channel Islands being the only locality. In Guernsey this species is found in just one hedgebank where it proliferates in disturbed patches. The fronds are small at around 2-3cm, the individual plants can form sizeable clumps however and this year it seemed to be doing especially well due to favourable climatic conditions. Typically the sporophyte stage lasts from around November to May but climate does influence this.
N49º 27'1" W2º 36'10"
