Development of ovule and seed coat in Cneorum tricoccon L. (Cneoraceae)

The ovule primordium of Cneorum tricoccon is trizonate. The ovule is anatropous, bitegmic and crassinucellate with a massive parietal tissue. The inner and outer integuments are both of dermal derivation and initially 2-layered, but the inner integument later becomes about 4-layered and the outer one 4 to 5-layered. The seed coat structure is described for the first time. The fruit wall has taken over the protective function of the seed coat. The testa shows but few differentiated layers, the exotesta develops thickened outer walls, and the meso-endotestal cells are rounded and somewhat thick-walled. The other layers of the seed coat become almost completely crushed and resorbed. A distinct micellar cuticle and nucellar remains are present at the inside of the seed coat. The seed turns strongly campylotropous as a result of differential growth from the raphal region and by the strong enlargement of the antiraphal side. The ovule and seed characters support the Rutalean relations of the family Cneoraceae.