1 8 Introduction to Botany. 



there before ; and that treeless areas along the borders of 

 streams soon become overgrown with dense groves of 

 Cottonwood and willow sapHngs after cattle are excluded, 

 the seeds in some instances having come several miles 

 from the homes of their ancestors. 



8. Food and Protection. — In order fully to understand 

 the significance of the various structures of a seed, we must 

 keep in mind its functions of continuance, migration, and 

 multiplication, and the conditions under which these func- 

 tions must be performed. It is of great importance that 

 the young plant in the seed be protected against unfriendly 

 contingencies. We find that mechanical injuries are pre- 

 vented either by the extreme hardness of the embryo and 

 reserve food, as in the case of Lima bean and Indian corn ; 

 or, if the embryo and reserve food are oily and soft, by a 

 covering of stony hardness, such as the castor bean and 

 various nuts possess. The reserve food materials are 

 packed tightly into the seed, and in a form which is, for 

 the most part, insoluble in water, and on that account 

 more certain of preservation within the seed. 



In some seeds the reserve material is stored entirely 

 within the embryo, as in Lima bean ; in others it is partly 

 within and partly without the embryo, as in Indian corn ; 

 while in others, such as the castor bean, it lies wholly out- 

 side the embryo. But this variation in the location of the re- 

 serve food seems to have little significance so far as concerns 

 germination, for in all cases it is finally transferred to the 

 growing parts of the seedling ; and whether this takes place 

 before the seed is cast from the parent plant, or only during 

 the stages of germination, is apparently indifferent to the 

 well-being of the young plant. The facts of significance 

 are, that the embryo plant is alive, although in a tempo- 

 rary state of inactivity ; that it has a sufficient store of 



