Prophase and Cytokinesis in Basal Streptophyte Algae Compared to Vascular Plants. Generalized scheme focusing on the main microtubule assemblies. Cytokinesis proceeds centripetally in the algae, but centrifugally in the vascular plants. Note that centrosomes and astral microtubules are absent from vascular plants. Microtubules (red bars), nuclei (purple), centrosomes with centrioles (encircled by blue rings).