XVI International Botanical Congess

We studied the ovule of A. altissima by light microscopy. There is anarchesporial cell with three parietal cells in the nucellus at the time ofinner integument initiation. The outer integument appears after the innerone, and never reaches the micropyle. The chalazal megaspore gives rise to a Polygonum type megagametophyte. After periclinal divisions, there are eight parietal cells and a nucellar cap with up to nine cell layers. Inthe chalaza, a deposition of tannins first occurs near the base of the inner integument, then occupies the whole chalazal plate, and later finally extends (with traces of cutin) in a conical form in the nucellus down to the chalazal end of the megagametophyte. The mature ocule is somewhat curved in the micropylar end, but we consider that the ovule is hemianatropous.