Pals et al. 1980: leaf spines, consisting of a single thickened cell, narrowly elongate and sharply pointed, bearing at its base the impression of attachment to adjacent cells.
Pals JP, van Geel B, Delfos A (1980) Palaeoecological studies in the Klokkeweel bog near Hoogkarspel (prov of Noord-Holland). Rev. Palaeobot. Palynol. 30:371-418.