Since the endophyte is disseminated only by seed, the life cycle is relatively simple (Bacon and Siegel, 1988; Welty et al., 1986). The fungus moves from the germinating seed into the seedling and colonizes mainly leaf sheaths, meristems, and internodes of elongating stems, but not roots (see Chapter 14). The endophyte colonizes developing seeds after anthesis, where it remains until the seed are planted and germinate, or it dies in storage. Several ergot alkaloids were isolated from E- plants (Lyons et al., 1986; Bacon and Siegel, 1988), and ergovaline was deduced to be the one most responsible for animal toxicosis (Lane et al., 1997). However, recent research (Hill et al., 2001) indicated that transport of the ergopeptine alkaloid ergovaline across ruminal gastric tissue is low as compared with the simple ergoline alkaloids, lysergic acid and lysergol. Multiple forms of ergot alkaloids circulate in livestock suffering from fescue toxicosis; this diversity may account for the numerous physiological symptoms of the disorder (see Chapter 12). Identifying the toxic agent or agents responsible for fescue toxicosis may lead to pharmacological or feed additive treatments as remedies.