Roles for oligosaccharides as signals for activating defensive and de­ velopmental processes have continued to be reported and supported in the recent literature. Studies of recognition events employing defined oligosac­ charides indicate that oligosaccharides interact with cellular membrane recep­ tors in a hormone-like manner to affect gene regulation. Recent studies concerning the regulation of signal production (e.g. studies of the roles PGIPs play in regulating the effective half-lives of oligouronides in infected tissue; and investigations of possible roles for cell wall fragments in morphogenesis, hypersensitivity, fruit ripening, and cell elongation) provide further evidence that oligosaccharides signal developmental responses. In plants, as in an­ imals , our understanding of how complex carbohydrates may function i n signaling and recognition systems is still in its infancy.