A histogram showing projection patterns of mitral cell axons in response to Slit-expressing cells and RoboN. E12.5 whole-telencephalon preparations were organotypically cultured for 2 d under various conditions and classified into five groups according to the projection patterns of mitral cell axons as follows: axons form the LOT bundle >100-μm-wide; axons form the LOT bundle 20- to 100-μm-wide; some axons elongate throughout the entire LOT pathway but only form a bundle <20-μm-wide; axons stall halfway along the LOT pathway as in Figure 2H; and axons that are repelled away toward the olfactory bulb as in Figure 2,D and F. Solid barsindicate the number of explants cultured without transplantation of Slit-expressing cells in normal culture media. Hatched bars indicate those transplanted with Slit-expressing cells and cultured in the presence of RoboN. Open bars indicate those transplanted with Slit-expressing cells and cultured in normal culture media. Slit-expressing cells strikingly repel and inhibit the growth of mitral cell axons, but the effects are blocked by RoboN.