Lycopodium alpinum also known as Diphasium alpinum; The Alpine Clubmoss has upright fertile branches with terminal spikes of sporophyllia (leaves that have spore-forming organs) which are only about 10-15 cm. Infertile branches creep along the ground. The plant seems to grow well where there is abundand snow in winter. Thus it is more common in the north and confined to the mountains of the south-west and south-east in the souhtern part of Iceland. On Iceland it is known as Litunarjafni.
How to recognize common Iceland clubmosses:
1) No trailing stems and no "cones on top of stems", leaves needle-shaped with smooth margins :
Lycopodium selago (= Huperzia selago), fir clubmoss
else: go to 2)
2) No trailing stems but sporophyls (leaves with spore-forming organs in the axis of leaf and stem) on top of stems, leaves are toothed:
Selaginella selaginoides, Lesser Clubmoss
else: go to 3)
3) Long prostrate stems ("runners") and sporophyllia on top of ascending brances;
3a) leaves of ascending branches pressed on the stem:
Lycopodium alpinum, Alpine Clubmoss; this card
3b) leaves of ascending branches spreading from stem:
Lycopodium annotinum, Interrupted Clubmoss
Very rare on Iceland is Lycopodium clavatum - of western Europe. It is much like Lycopodium annotinum but characteristically has a stem segment between the vegetative parts and the sporophyl-bearing part which has very small leaves, making this intersegment stem look almost nude. Split on top of this segment are two sporangial stems (hence the name clavatum).