\So"rus\, n.
   (a) In parasitic fungi, any mass of spores bursting
       through the epidermis of a host plant.
   (b) In lichens, a heap of soredia on the thallus.

\So"rus\, n.; pl. {Sori}. [NL., fr. Gr. ? a heap.] (Bot.)
One of the fruit dots, or small clusters of sporangia, on the
back of the fronds of ferns.