462 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1956 



betray their origin to the casual observer. Take the grasslands of 

 California, the rolling hills back from the coast, the oak-dotted savan- 

 nas of the Great Valley. Here are stretches of what look like indige- 

 nous vegetation. Much of this mantle is not obviously tended by man ; 

 it has the look of something that has been in California as long as the 

 oaks it grows among, yet the bulk of it came, all uninvited, from the 

 Old World along with the Spaniards. Most of it had a long history 

 of association with man when it made the trip. Wild oats, wild mus- 

 tards, wild radishes, wild fennel — all of these spread in from the 

 Mediterranean, yet over much of the California cattle country they 

 dominate the landscape. Native plants are there, even some native 

 grasses, but it takes a well-informed botanist going over the vegetation 

 item by item to show how small a percentage of the range is made up 

 of indigenous California plants. 



For those parts of the Tropics where plants grow rapidly it will take 

 careful research before we can have an informed opinion about such 

 questions. Thorn scrub, savannas, bamboo thickets, weedy tangles of 

 quick-growing trees and shrubs are known to have covered vast areas 

 in the last two or three millenniums. Yet Standley, our greatest 

 authority on the vegetation of Central America, digging up a small 

 tree in what appeared to him to be a truly indigenous forest in the 

 Lancetilla Valley, came upon a layer of potsherds (Standley, 1931). 

 What is the relation between the supposedly wild avocados of such a 

 forest and the avocados eaten in the village that once covered that 

 site? We now have various techniques (pollen profiles, carbon-14 

 datings, chromosome analysis, extrapolated correlates) which can give 

 critical answers, but they are time-consuming, and their application 

 to such problems has just begun. 



The total number of plants and animals that have moved in with 

 man to any one spot on the earth's surface is way beyond what even 

 a biologist would estimate until he looked into the problem. There 

 are the cultivated plants both for use and for display, the domesticated 

 animals, the weeds, and their animal equivalents such as houseflies, 

 clothes moths, rats, and mice. A much larger class comprises organ- 

 isms not purposely introduced by man, which are neither eyesores 

 nor plagues, but which, like weeds, have the capacity to get along 

 in man's vicinity. Such are the daisies and yarrows and buttercups 

 of our meadows. Such, in a sense, are even those native species that 

 spread under man's influence. Take, for example, the sunflowers of 

 Wyoming. They are certainly native to North America and may pos- 

 sibly in part be prehuman in Wyoming. They line the roadways yet 

 seldom are elsewhere prominent in the native landscape. They ap- 

 peared along with the road, even though they may have moved in from 

 not so far away. But how did they get into the spot from which they 



