series entitled Experimental Studies on the Nature of Species. 

 The trio consisted of Jens Clausen, a Danish cytologist (a biolo- 

 gist who investigates chromosome number, structure, and behav- 

 ior), William Hiesey, a plant physiologist, and David Keck, a plant 

 taxonomist. These three men worked at the Carnegie Institution 

 of Washington's Division of Plant Biology housed on the Stanford 

 campus. The Carnegie group established three gardens which 

 provided the growing grounds for some of their experimental 

 plants. These gardens are located at Stanford, Mather, and 

 Timberline. 



The Stanford garden is situated in the South Coast Ranges at 

 an elevation of about 90 feet (27 m). The natural vegetation of 

 this area is (or was) oak savanna, which belongs to the Valley and 

 Foothill Woodland plant community. The average growing season 

 here is about 280 days. There is no winter snow and freezing 

 temperatures are uncommon. The average rainfall is about 12.5 

 inches (32 cm) per year, most of which falls in the winter. The 

 summer is dry and relatively warm. 



The second garden, at Mather, is on the western slope of the 

 Sierra Nevada. The elevation of this garden is somewhat over 

 4,000 feet (1,219 m). It is located in a well-developed coniferous 

 forest which belongs to the Montane Forest plant community. 

 The growing season here is 145 days long and there are moderate 

 winter snows. The annual precipitation averages 38.5 inches 

 (98 cm) and, although July, August, and September are generally 

 dry, occasional rains may fall during these months. 



The third garden is at a locaUty called Timberline, which is 

 just east of the crest of the Sierra Nevada at an elevation of over 

 9,000 feet (2,743 m). This is an alpine area located in a montane 

 meadow near the vegetational timberline. The growing season 

 here is only 67 days long and there are heavy and prolonged 

 snows in the winter months. Precipitation is 29 inches (74 cm) of 

 rain and snow per year, and there is no distinct dry season 

 during the summer. 



The Carnegie group was interested in learning how certain 

 widely distributed plant species are adapted to the climatic regime 

 that occurs over much of California. They selected as their ex- 

 perimental plants some relatively widely distributed species which 



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