Fig. 8. Taste buds only form when presumptive pharyngeal endoderm is fused with presumptive axial mesoderm. Endoderm alone (Endo) is devoid of taste buds and differentiated mesoderm. Mesoderm alone (Meso) lacks taste buds (striped bars), but develops notochord (gray bars) and muscle (black bars). When these two regions are fused (Endo+Meso), now all explants generate all three differentiated tissues. Intermediate regions (Int) cultured alone typically generated mesodermal derivatives, and reasonably frequently gave rise to taste buds. Sample sizes are above histogram bars.