Ricerche Cariologiche e Embriologiche Sul Genere Rudbeckia (Asteraceae)

Abstract

The author describes the different modalities of the cellularisation of the adult gametophyte of Rudbeckia laciniata L. The several cases are arranged according to the number and the type of differentiation of the cells of the gametopyte. Of each type it is stated the frequency, calculated in about 500 cases. The author remarks that the differentiation of the single cells is owing to »an effect of the position«, which exists in the displacement of the nuclei of the gametophyte regarding the proendospermatic cell, to which cell, however, one can attribute a pre-eminent »power of organization«. The displacement of the nuclei is after all the consequente of the stage of the » polarisation «.