This thesis comprises three parts each of which encompasses one component of the researcher: conducted between 1995 and the present. Chapter I briefly defines secondary plant compounds and describes their possible roles and uses. I have included this chapter to show commonality. In my investigations of Albizia julibrissin and Asclepias subverticillata, and how the study of secondary plant metabolites brings together the many disciplines of organic chemistry, biochemistry, pharmacology, toxicology, plant taxonomy, and ecology. Chapter II describes the investigation of a neurotoxic alkaloid found in Albizia julibrissin (mimosa). Chapter III describes the investigation of the neurotoxic compounds present in Asclepias subverticillata (western-whorled milkweed). Chapters II and III will be submitted for publication in Poisonous Plants, Proceedings of the 5th International Symposium on Poisonous Plants and the format of each is that required for submission. The format of Chapter I follows that of Chapters II and III in order to have continuity within the thesis. Sincere appreciation is expressed to Dr. Ronald J. Tyrl, my major advisor, for his loyal, patient dedication to the advancement of knowledge. His guidance, understanding, and iii friendship have greatly assisted me achieving my academic goals. Special gratitude also is expressed to committee members Dr. George E. Burrows and Dr. Elizabeth M. Holt. Their assistance, patience, and forthrightness have been greatly appreciated. Sincere appreciation also is conveyed to Dr. A. Daniel Jones, Director of the Facility for Advanced Instrumentation at the University of California, his time and spectrometric expertise on subverticilla ta. Finally, an enormous thank Davis, for Asclepias you to my husband, Randy Robinson, for his advice, support, and patience during this exploratory period of my life.