Yesterday’s gathering was very successful with a dozen attendees. We visited some Polypodium sites in Portree and then undertook some microscopy to check the species. We saw both Polypodium interjectum (Intermediate Polypody) and Polypodium vulgare (Common Polypody), but no sign of the hybrid.
Cards like these were available
with the reverse including these words:
“Skye’s PLANT project needs your help to find and record a type of fern called Manton’s polypody. Spotting polypodies is quite easy but telling the three kinds apart is a bit of a challenge. If you need help with identification join a free ID session.
Find out about regular free identification sessions by contacting: skyebotanicalrecording@gmail.com. Confident with ID? Then submit records online here.” Actually, I have changed the link from what it says on the card, but this takes you to the right place.
Back home, here are photomicrographs of sporangia from the two species on Raasay:
At this time of year, the best way to tell these two species apart is to scrape some sori onto a microscope slide and count the number of cells in the annulus with thick walls. The annulus is the partial ring of cells that is involved in spore dispersal – the ones with thickened walls dry out, shrink and pop the thinner-walled cells on the opposite side of the sporangium. On the left is P. vulgare with about 12 of these cells, and on the right P. interjectum with more like 7.
The spores of P. interjectum are significantly larger than this of P. vulgare though otherwise similar, but if you have a calibrated eyepiece with graticule, this is also an excellent way of differentiating the two species.
There will be a second part to this project concerning Ophioglossum (Adder’s-tongue) species, starting in April.
Plants of Skye, Raasay & The Small Isles 