Fig. 6. Requirements for fng and Notch in stalk cells. (A-C) fng¹³ or (D) N^55e11 clones marked with -Myc (green) and stained for nuclei (white or blue) and P3F or FasIII (B,C, red). (A) Stalk with eight fng^- cells and 1 fng⁺ cell (white dot). Although FasIII staining is never detected in fng^- cells in the follicular epithelium, it persists in fng^- cells in the stalk. Arrow points to polar cells. (B) Stalk with 11 cells, four are fng⁺. All express 93F (arrowhead). Arrow indicates a gap into the follicle epithelium, presumably due to the absence of polar cells. The adjacent stalk cell is fng⁺ (arrowhead). (C) Stalkless follicles with four 93F-expressing cells (arrowhead). (D) Stalk with >15 cells that is mosaic for Notch.