Nuclear pores have been studied with the electron microscope in thin sections of pollen mother cells at early- to mid-meiotic prophase (a) in respect of distribution, (b) in relation to fine structure in the pore complex in the following plants: Fritillaria lanceolata, Phaedranassa viridiflora, Tulbaghia violacea, an F<latex>$_1$</latex> hybrid of Allium fisultosum x Allium cepa and the lily var. 'Formobel'. In all plants from leptotene to pachytene, the pores were irregularly spread over the envelope in random clusters of variable size encircled by areas in which they did not occur. Further proof was obtained from the lily for the premise that pores are not formed in regions of the envelope to which the nucleolus is adpressed at leptotene. The fine structure of the pore complex observed supports a model which proposes that annuli are composed of three rings of eight granular subunits. Most pores contained a central granule ranging from 25 to 30 nm in diameter composed of amorphous substance and filaments about 3 nm wide, apparently continuous with filaments of similar dimensions in the symmetrical annular subunits that encircle the orifice at both the nuclear and cytoplasmic sides of the pore. The pore complex and central granule were relatively more stable to osmotic shock than the ribosomal region of the nucleolus. Recent ideas concerning the role of the annulus and central granule in nucleocytoplasmic transfer of ribonucleoprotein and assembly of polyribosomes are discussed.