Pran Nath Mehra obtained his DSc (1942) from Panjab University, Lahore specializing in cytology and morphology of bryophytes and vascular plants, medicinal plants, tissue culture and morphogenesis. He served as the Research Advisor, Himachal Pradesh Agricultural University; Honorary Professor, Tribhuvan University, Nepal; Senior Professor and Head, Department of Botany and Director, Centre of Advanced Studies and later Professor Emeritus, Panjab University, Chandigarh. Academic and Research Achievements: Mehra put forth a new theory, known as ‘condensation theory’, on the origin and evolution in Hepaticeae, which has been widely accepted all over the world. He had done extensive work on: phyletic classification of ferns; cytogenetic evolution in hardwoods based upon investigations on more than 500 species of trees in the Himalayas, considered to be the most comprehensive investigation of forest trees in the world; and induced meiotic reductions in root-tips. Also put forth a saturation hypothesis for the absence of polyploidy in conifers and gene block hypothesis as applied to ferns and flowering plants. Other areas in which Mehra had made contributions are phyletic evolution of grasses, and distribution of Prodocarpean flora and the concept of Gondwanaland. Other Contributions: Mehra was the Member Advisor, Indian Pharmacopoeia Committee; Member, Advisory Board, Botanical Survey of India and Zoological Survey of India, Advisory Board of Agriculture (Government of India), Expert Committee on Pharmacognosy and Pharmacology (ICMR); and many other bodies. He was the author of nine research monographs, reviewed by specialists as very significant contributions and served as member of editorial board of The Wealth of India (CSIR). He was the Member, INSA Council (1969-70). Awards and Honours: Mehra received the Birbal Sahni Gold Medal (1968), UGC National Lecturer (1970), International Botanical Congress Medal as Vice-President (1975); Gunner Erdtman International Gold Medal (1975); Sunder Lal Hora Medal (INSA) (1984); Tree scientist Gold Medal (1984); Birbal Sahni Centenary Commemoration Lecture Award and Gold Medal (1992); Padma Shri (1972); Sir Charles Seward Memorial Lecture (1967); Gregor John Mendel Memorial Lecture (1968); Panchanan Meheshwari Lecture (1968); Philip R White Memorial Lecture (1971), Chavan Memorial Lecture (1973); Joshi Memorial Lecture (1974); Street Memorial Lecture (1987) and Birbal Sahni Centenary Commemoration Lecture (1992). Mehra was a Fellow of National Academy of Science (India), Allahabad, Indian Botanical Society, Indian Palynological Society, Indian Society of Tree Scientists, and Indian Society of Pharmacognosy; Corresponding Member, Botanical Society of America.