Diversity within and among living organisms is both a biological impera tive and a biological conundrum. Phenotypic and genotypic diversity is the critical currency ofecological interactions and the evolution of life. Thus, it is not unexpected to find vast phytochemical diversity among plants. However, among the most compelling questions which arise among those interested in ecological phytochemistry is the extent, nature, and reasons for the diversity of chemieals in plants. The idea that natural products (secondary metabolites) are accidents of metabolism and have no biological function is an old one which has resurfaced recently under a new term "redundancy. " Redundancy in the broader sense can be viewed as duplication of effort. The co-occurrence of several classes of phytochemieals in a given plant may be redundancy. Is there unnecessary duplication of chemical defense systems and ifso, why? What selective forces have produced this result? On the other hand, why does the same compound often have multiple functions? At a symposium of the Phytochemical Society of North America held in August 1995, in Sault Ste. Marie, Ontario, Canada, the topic "Phytochernical Redundancy in Ecological Interactions" was discussed. The chapters in this volume are based on that symposium. They both stimulate thought and provide some working hypotheses for future research. It is being increasingly recognized that functional diversity and multiplicity of function of natural products is the norm rather than the exception."

This issue of Otolaryngologic Clinics, guest edited by Drs. James E. Saunders, Susan R. Cordes and Mark E. Zafereo, is devoted to Global Health in Otolaryngology. Articles in this outstanding issue include: Surgical Care and Otolaryngology in Global Health; Otolaryngology and the Global Burden of Disease; Health Organization and Otolaryngology; Otolaryngology in Low-Resource Settings: Practical and Ethical Considerations; Using Technology in Global Otolaryngology; Educational Resources for Global Health in Otolaryngology; Global Hearing Loss Prevention and Services; Management of Chronic Ear Disease and Otosclerosis; An Evidenced-Based Practical Approach to Pediatric Otolaryngology in the Developing World; Outcome of Head Neck Squamous Cell Cancers in Low Resource Settings: Challenges and Opportunities; Thyroid Disease Around the World; Workforce Considerations, Training and Diseases in Africa; Workforce Considerations, Training and Diseases in Latin America; Workforce Considerations, Training and Diseases in Asia/Pacific; Workforce Considerations, Training and Diseases in the Middle East; Workforce Considerations, Training and Diseases in Europe; and Overview of Otolaryngology-related Disorders in Underserved Populations, Otolaryngology Training, and Workforce Considerations in North America.

Diversity within and among living organisms is both a biological impera tive and a biological conundrum. Phenotypic and genotypic diversity is the critical currency ofecological interactions and the evolution of life. Thus, it is not unexpected to find vast phytochemical diversity among plants. However, among the most compelling questions which arise among those interested in ecological phytochemistry is the extent, nature, and reasons for the diversity of chemieals in plants. The idea that natural products (secondary metabolites) are accidents of metabolism and have no biological function is an old one which has resurfaced recently under a new term "redundancy. " Redundancy in the broader sense can be viewed as duplication of effort. The co-occurrence of several classes of phytochemieals in a given plant may be redundancy. Is there unnecessary duplication of chemical defense systems and ifso, why? What selective forces have produced this result? On the other hand, why does the same compound often have multiple functions? At a symposium of the Phytochemical Society of North America held in August 1995, in Sault Ste. Marie, Ontario, Canada, the topic "Phytochernical Redundancy in Ecological Interactions" was discussed. The chapters in this volume are based on that symposium. They both stimulate thought and provide some working hypotheses for future research. It is being increasingly recognized that functional diversity and multiplicity of function of natural products is the norm rather than the exception.

The influence of compounds in the environment on the chemistry of plants is a topic which has economic and scientific implications of global importance. Selected presentations in this symposium covered several topics within this immense field, inclusive of air, soil, and aquatic sources of the compounds. As demonstrated in Chapter 4 by O'Keeffe et al. we have not restricted the discussion solely to negative aspects of anthropogenic compounds. Nor could we begin to cover comprehensively all major classes of environmental compounds in the air, soil or water that may have an effect on the phytochemistry of plants. Our intent was to focus on some of the timely and well publicized environmental constituents such as ozone, sulfur dioxide, acid rain, and others, to provide an authoritative publication specifically related to environ mental modifications of plant chemistry. The concept of this symposium originated with the Executive Committee of the Phytochemical Society of North America in 1983. It was brought to fruition during July 13-17, 1986 on the campus of the University of Maryland at the annual meeting of the PSNA through the efforts of the Symposium Committee composed of James A. Saunders and Lynn Kosak-Channing. Financial support for this meeting was provided by the Phytochemical Society of North America, as well as by generous contributions from E. I. du Pont de Nemours & Company and the U. S. Department of Agriculture. The Organizing Committee, consisting of J. A. Saunders (Chair), J. M. Gillespie, L. Kosak-Channing, E. H. Lee, J. P."