Ophioglossum vulgatum in my polytunnel

About 20 years ago I was given a piece of turf about 12 x 6 x 6 inches containing (amongst other plants) Ophioglossum vulgatum
This turf was given to me by Nigel Brown from the land belonging to Bangor University
I planted it in my polytunnel at my allotment in Portsmouth
These plants have done very well and appear in April and do not disappear until late October
Many of my plants have curious sporangiferous spikes

You can find an interesting article here