282 Plant Life and Evolution 



more or less unpleasant experience, discovered the 

 narcotic properties of opium and tobacco, the stimu- 

 lating effects of tea and coffee, the cathartic quali- 

 ties of various seeds and barks. While medicinal 

 plants must be considered of much less importance 

 than the staple food plants, still they are in many 

 cases of very great value, as for instance quinine, 

 which has made it possible for white men to live 

 in certain fever-stricken regions in the tropics where 

 otherwise they could not have existed. 



The last category of useful plants comprises those 

 grown for constructive purposes, like timber trees 

 and bamboo, but even at the present day the supply 

 of timber is largely drawn from natural forests 

 tree planting for timber being a recent development, 

 but one of rapidly growing importance and likely 

 to affect strongly the character of large tracts of 

 country in the United States and elsewhere. . . . 



Just when the first attempts at agriculture were 

 made is not known, but it is evident from historical 

 record that in all the ancient civilizations of which 

 we have any trace, many plants were regularly culti- 

 vated. Thus in ancient Egypt wheat and flax were 

 grown, and in China, 5,000 years ago, there is evi- 

 dence that rice, wheat, sweet potatoes, and millet 

 were cultivated. In America, long before its dis- 

 covery by Europeans, Indian corn, potatoes, and 

 tobacco, and other plants were regularly grown, 

 but very little is known of the exact age of these 

 early civilizations in South America and Mexico. 



