included the Yarrow (Achillea, Compositae, Plate 4A). Since the 

 taxonomy of the Achillea is a bit complex, it is sufficient to say 

 that this plant belongs to the Achillea millefolium group. For 

 our purposes, we can consider that it consists of a single species 

 in the area studied. 



Seeds of Achillea were collected from natural populations 

 distributed across California from the sea coast to the alpine 

 regions. Seedlings from these wild plants were grown at Stanford 

 and each of 60 seedlings was subdivided into three rooted cut- 

 tings. One cutting from each seedUng was planted in the Stanford 

 garden, one at Mather, and one at TimberUne. The three individu- 

 als obtained in this manner from a single parent together con- 

 stitute a clone, which is a term that refers to all individuals vege- 

 tatively propagated from a single "mother" plant. Each of the 

 60 seedlings was cloned, and the result was that each of the 60 

 individuals at Stanford had an identical mate at Mather and at 

 Timberline. Use of the clone method enabled Clausen, Keck, and 

 Hiesey to study the behavior of 60 "individuals" grown in three 

 different places at once. 



After a suitable time interval, the Carnegie group started the 

 first of a series of measurements of the plants in the three gardens 

 to determine their responses to the different climatic conditions 

 that prevail in these three locaUties. 



Although several characteristics were measured and several 

 populations were studied, the following synoptical table gives 

 measurements for three characteristics of four sample popula- 

 tions of Achillea, since this condensed version of the extensive 

 experiments suffices for illustrative purposes. All figures given 

 in the table are means. The term "Bodega population" refers to 

 plants that originated near Bodega Bay, Sonoma County, an area 

 on the immediate coast of northern California not far from San 

 Francisco. The Clayton population came from the vicinity of 

 Clayton, Contra Costa County, near Mount Diablo, which is at 

 the edge of the Central Valley east of San Francisco. The Mather 

 population originated at Mather in the vicinity of the Mather 

 garden in the Sierra foothills. Big Horn Lake is over the crest 

 of the Sierra Nevada at approximately 1 1 ,000 feet (3,353 m). 

 Its climatic regime is similar to that of TimberUne. 



49 



