THE STORY OF SEEDS 249 



the plant kingdom as we see it to-day is a result of the 

 great tendency of plant life to spread and multiply. 



To keep alive and to multiply, then, are the two great 

 laws of plant life. The former we call nutrition; the 

 latter reproduction. 



Now, as plant life went on in those ancient days it kept 

 improving. The two great problems of plant life have 

 always been the same, but the plant's ways of solving these 

 problems have changed. It is as though the plant king- 

 dom kept inventing better ways of doing its work. All 

 this took a great deal of time. Plants are changing now 

 just as they changed in the past, but the changes are so 

 gradual that we hardly notice them. Yet you know that 

 the fruits we have in the market to-day are much better 

 than the fruits our grandfathers had. This shows that 

 plants change, and that these changes can be controlled 

 by man. What we want "o do now is to consider some of 

 the ways in which plants have changed in the past, and 

 we do this so that we can understand plants as we see them 

 to-day. 



Reproduction. There was that ancient little plant that 

 had to reproduce. It did it in the simplest possible way. 

 It just divided into two. Then each of the two new plants 

 (daughter-cells) divided again, and so on. It was very 

 simple, and it is a method of reproduction that is still 

 used. But it was not enough. Plants simply had to grow, 

 and expand. Tiny, round, one-celled plants could never 

 spread over the land. They would dry out too quickly. 



We often find growing in running water plants that are 

 composed of slippery green threads. They belong to the 

 group of plants called alga. Surely you have seen them 



