476 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1956 



journals and in books for the intelligent public. They allow us 

 (through a meticulous examination of variability in such mongrel 

 complexes as the salvias of the abandoned olive orchard) to determine 

 precisely the good species (or subspecies or varieties) from which 

 these complexes must ultimately have arisen. Furthermore, though it 

 takes considerable hard work, these methods can be used successfully 

 by one with no previous knowledge of the organisms or of the faunas 

 and floras from which they may have come. 



Using these methods, I have shown that the common Adenostoma 

 fasciculatum of coastal California arose from the hybridization of 

 two very different adenostomas. One of these was A. fasciculatum 

 var. obtusifolium, a low-growing shrub of the headlands and islands 

 along the California coast. The other is now found in its purest form 

 in the Mother Lode country of the Sierra foothills, a tall, branching 

 shrub which, when in flower, somewhat resembles a small-leaved white 

 lilac. Each of these had its own contributions to make to life in 

 coastal California. The coastal shrub brought in a tolerance of bril- 

 liant sunlight and the ability to grow in thin, rocky soil. However, 

 it was accustomed to fog and drizzle even during the dry season. The 

 inland form could go months without a drop of water, but it is used 

 to deeper soil and to less extreme radiation. When these two centers 

 of variation had been identified, it was easy to demonstrate that the 

 common Adenostoma is a great, plastic, hybrid swarm, including ap- 

 proaches to these two extremes and many intermediates between them. 

 On dry, rocky ridges in sites that are frequently foggy, one finds plants 

 very close to the island extreme. On deeper soils and in the shade 

 of small oaks are bushes scarcely different from those of the Mother 

 Lode country. Around old ranch buildings and in other peculiar 

 habitats one finds strange and bizarre recombinations of various sorts. 



Just as these studies came to a close and it was time for me to leave 

 California, I realized that many of the other plants in the chaparral 

 association were similarly variable. There were swarms of hybrid 

 oaks and hybrid ceanothus and hybrid manzanitas. The entire asso- 

 ciation seemed to be in a state of flux. Unlike the coastal sages which 

 I had studied in southern California, there was room for hybrid re- 

 combinations within the association itself. The entire chaparral 

 seemed to be ecologically in the same general class of disturbed habitat 

 as the abandoned olive orchard. 



I do not wish to jump to conclusions from one small experiment. I 

 would merely suggest that these methods are appropriate for the anal- 

 ysis of such problems, particularly if combined with experimental 

 work (for instance, the removal of a single species or species complex 

 from a small area using modern herbicides followed by measurement 

 of the effect of this removal on the other complexes in the association) . 



