6 INTRODUCTION 



would see men at work, the grain already piled in shocks. 

 On hiUs and near streams you would see cattle grazing in 

 the pastures, gathering their food from plants. 



That great view of fertile country would delight you. 

 Perhaps it would set you thinking. You might think of 

 the miracle of nature by which this huge harvest has 

 come from tiny seeds. You might think of the thousands 

 of acres needed to yield food for one small city. You might 

 think how small man is in the midst of the millions of plants 

 which sustain him. You might think of the soil, that 

 wonderful and complex layer which covers the rocks and 

 holds, firmly and nourishingly within itself, the roots of 

 plants; it is of the soil we think when we say " Mother 

 Earth," for it is the soil which permits Earth to be 

 " mother " of us all, plants and animals ahke. As you 

 looked down upon the great green carpet of plants below, 

 you might remember that your own life depends upon this 

 green life of plants, and perhaps you would feel grateful. 

 At least you would enjoy its beauty, and might wish to 

 know more about it. 



Or suppose you were on a ship coming near to the steep 

 shore of some tropical island. There vou would see no 

 sign of men, but high above you would stretch hill and 

 mountain sides, covered with the deep green of tropical 

 forests, only the bare white trunk of a tree showing here 

 and there. All the land would be hidden, the year round it 

 is hidden, under this heavy mantle of plant growth. Trees 

 you would see ever3rffhere, trees even growing out to sea, 

 as is a habit of some trees in the tropics. Coming nearer, 

 you might see little houses along the shore, but all the 

 work of men would be a trifle compared with the mass of 

 vegetation surrounding it. And so wherever you go in 



