Digestion and Fragmentation: Influence on Herbivore Diet Analysis

positions of ingested and excreted mixtures (Hansen et al. 1973, Todd and Hansen 1973). A discernible plant fragment can be identified, but discernibility varies among plants and may be a significant source of error in quantification. Leaves are composed of epidermis, mesophyll, and vascular bundles. Epidermis is covered by indigestible cutin that inhibits digestion of mesophyll by blocking passage of microbes into the leaves (Harbers et al. 1981). There are no known microorganisms that produce cutin-degrading enzymes (FreyWyssling and Muhlenthaler 1959). However, once passage is gained by maceration, mesophyll is readily degraded, whereas the epidermis and cells surround'This project was conducted under Cooperative Agreement 19-335 between the U.S. Forest Service, Southern Forest Experiment Station and the Mississippi Agricultural and Forestry Experiment Station. 2 Present address: School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge, LA 70803. 3 Present address: Department of Animal and Range Science, New Mexico State University, Las Cruces, NM 88003.