| Citation | Distinguished for his physiological and biochemical studies on nitrogen fixation by symbiotic systems and blue-green algae. His adaptation of the acetylene reduction technique for measurements in the field has led to a great expansion in knowledge of the ecology of nitrogen fixation. He has played a principal part in elucidating the role of the heterocyst in nitrogen fixation and his discovery that non-heterocystous species of blue-green algae may fix nitrogen under micro-aerophilic conditions is a major advance. He has also contributed significantly to knowledge of the pathology of blue-green algae and of the general ecology of the soit, freshwaters and estuaries. |