Development of ovule and testa of Geranium pratense L. and some other representatives of the Geraniaceae

The ovules and seeds of the genera Geranium, Pelargonium, Erodium. Monsonia, and Sarcocaulon are very similar. The ovule primordium of Geranium is trizonate. The outer and inner integuments are both of dermal derivation and initially only 2 cells thick, to become multilayered owing to mitotic activity in the inner cell layer. Shortly before fertilisation a development begins which ultimately results in a marked degree of campylotropy of the seeds. The mechanical layers consist of the sclerotised and crystal-containing cells of the inner epidermis of the outer integument, and sclerotised cells of the outer layer of the inner integument which are star-shaped in surface view. Nucellus and endosperm have disappeared almost completely in the mature seed. In several representatives of the family the seed-coat contains stomata.