82 READINGS IN BIOLOGICAL SCIENCE 



But the West is relatively poor in broad-leaved trees. Climatically, eastern 

 Asia, including much of Japan, is also similar to eastern North America. 

 Consequently, it is logical to find that these two regions both show brilliant 

 colors. 



On the other hand, much of northern Europe has cool, damp, cloudy 

 weather in the fall. This is not so true farther south, so that in the Danube 

 valley beautiful foliage does occur. In parts of the Alps, due mostly to 

 shrubs, the colors are also pronounced. 



Continental Europe, furthermore, does not have the wealth of broad- 

 leaved trees that occurs in eastern North America, though many of the 

 missing species will grow there if planted. In fact, many of them are found 

 in Europe in fossil form. When the glaciers came down from the north 

 in the last ice age, the plants in North America advanced south before 

 them. Our mountain ranges run north and south, so that this was possible. 

 In Europe, when the ice sheets came down, the flight of the plants was 

 impeded, since the mountain ranges run mostly east and west. Local moun- 

 tain glaciers advancing probably made the escape still more difficult, and 

 consequently many of the trees perished. The sweet gum, the tulip tree, 

 the hickory and the sassafras, for instance, grew in Europe until the last 

 glaciation. This is known from fossils. Partly because of climate and 

 partly because of the relative paucity of broad-leaved trees, Europe does 

 not have the display that we have here. Eastern Asia largely escaped the 

 last glaciation, while Greenland and Antarctica have not emerged from 

 it to this day. 



One topic more might be discussed — namely, the significance of colora- 

 tion in plants. It is well known and generally accepted that insects are 

 attracted to flowers partly on the basis of their color, though bees, like 

 many men, are red-green color blind. Young leaves unfolding in the spring 

 often show the same tints that are developed in the fall; and it has been 

 suggested that these pigments serve to absorb light and thus raise the leaf 

 temperature. Others claim that the pigments act as a protective screen 

 against certain rays of light that may be deleterious in various ways. 



While these last two explanations may possibly be of some significance 

 in autumn coloration, it seems hardly probable that the development of 

 these striking colors in the late fall is very important to the plant. The same 

 trees may get along perfectly well without them, and often do. It appears 

 more likely that the conditions are favorable, the stage is set, and the show 

 goes on, without any deeper significance. Perhaps this is the botanical 

 expression of "art for art's sake." In any event, it is a gracious way of say- 

 ing good-bye. 



