1.  calla(n = noun.plant) arum lily, calla lily, zantedeschia aethiopica - South African plant widely cultivated for its showy pure white spathe and yellow spadix;
is a kind of flower
is a member of genus zantedeschia, zantedeschia
has particulars: pink calla, zantedeschia rehmanii, golden calla

2.  calla(n = noun.plant) genus calla - water arum;
is a kind of liliopsid genus, monocot genus
is a member of araceae, arum family, family araceae

   A genus of plants, of the order Araceæ. [1913 Webster]
" The common Calla of cultivation is Richardia Africana, belonging to another genus of the same order. Its large spathe is pure white, surrounding a fleshy spike, which is covered with minute apetalous flowers." [1913 Webster]

calla, n.
1 (in full calla lily) = arum lily.
2 an aquatic plant, Calla palustris.

Etymology:
mod.L

black calla, calla lily, calla palustris, genus calla, golden calla, pink calla, wild calla