In search of allelopathy: an eco-historical view of the investigation of chemical inhibition in California coastal sage scrub and chamise chaparral

"He was certainly an inspiration for young students because he made them feel part of the 'grand battles' in which he always seemed to be engaged," Harold Mooney (1999) one of Muller's earliest students, wrote.

As a sophomore, Mooney listened to Muller reject allelopathy as he discussed Gray and Bonner's work on Encelia. Then, after a two-year stint in the US Army, Mooney returned to find his teacher "engaged in research that purported to demonstrate that allelopathy did indeed exist" in the foothills of Santa Barbara. "This was pretty exciting for a budding young ecologist, to see the stuff of science so close up: the proposal and counterproposal in trying to work out the complexities of the operation of natural systems."

"It was such an interesting time," Norm Christensen said when reflecting upon his work with Muller. "I look back on it all now and it was by far the best research I've ever done. It was so much fun. Behind his back, we affectionately knew C.H. as 'the gnarly'. We all loved his crustiness and knew well that he would march into the jaws of hell on our behalf. I am grateful to have had the opportunity to work with him. He is an exemplar of the fact that scientists are also very human. That's not a bad thing."

By the mid-1970's, Muller's deteriorating vision and brush with a near fatal illness made fieldwork impossible, but he continued writing research papers into the 1990's. In 1975, he was selected as the Ecological Society of America's Eminent Ecologist. The photo accompanying an article about the award shows the famous oak taxonomist with a wry smile holding a sprig of Toxicodendron diversilobum. (poison oak) (Fig. 3). V. Thomas Parker remembered, "He wanted to see if anyone would notice." In 1982, Current Contents, a source for bibliographic research, declared Muller's 1966 paper, "The Role of Chemical Inhibition in Vegetational Composition", a Citation Classic having been referenced more than 125 times.

As for others involved in the story, their paths diverged in a multitude of ways. Reed Gray, who co-authored the desert allelopathy paper with James Bonner in 1948, entered the private sector as a chemist after he was awarded a Ph.D. in biochemistry for his research on Encelia.

"That paper helped me all through my life in getting jobs and recognition," Gray said in 2003. "I remember the local Pasadena newspaper even did an article on it. It was titled something like 'the biochemical warfare among plants'."

The potential of using plant allelochemicals as herbicides prompted Gray to isolate and synthesize a toxic compound from the genus Leptospermum, commonly known as tea trees. He recorded two patents for the compound while working for the Stauffer Chemical Company in 1980. He is retired now, living with his family in Northern California.

Phil Wells went on to do pioneering work on the dramatic vegetation displacements of Great Basin forests since the last glacial period by using a unique source of information, fossilized remains of plants preserved in Neotoma (wood rat) nests occupied over the past 12,000 years (Wells 1983). "The idea first came to me when I spotted one of their nests at Indian Springs, near Las Vegas in the early 1960's. The material wood rats accumulate can be preserved for tens of thousands of years and contain samplings of all the plant communities existing around them," (Wells pers. com. June 03). Well's techniques are now the standard for studying Holocene and late Pleistocene paleoecology in arid parts of the world.