Students actively explore the nature of sexual differentiation in C-FERN®. Although all C-FERN® gametophytes develop from genetically identical spores, their development into males or hermaphrodites is environmentally controlled by a pheromone-like system. Students investigate this phenomenon experimentally by repeatedly inoculating culture dishes over a period of 7 days and analyzing the resulting sex ratios. They then formulate testable hypotheses to account for the presence and frequency of each sexual type in different aged inoculations. In addition to the wild type, this exercise uses a maleless stock (her1) that is insensitive to the pheromonal system. Includes materials for 30 students. Experiment time is 14 days. With instructions. Reusable with Replacement Set.