58 THE INVISIBLE WORLD 



the work of division and subdivision goes on until 

 millions upon millions of rootlets, as fine as fine 

 needles, pierce the soil in all directions for a large 

 distance around. 



Thus is formed a complete network of roots and 

 rootlets densely filling and occupying a large space 

 of ground. The different species of cells compos- 

 ing them are numbered by the thousands, per- 

 haps by the millions. Each species form multi- 

 tudes of colonies. Each colony, like a colony of 

 microbes, supplies its own aid in its own way. 

 Yet all the colonies are so related in their help 

 to one another as to make the entire mass of roots 

 and rootlets a firm and solid support to the full 

 grown oak. 



Meanwhile, the other tendency is upward. A 

 tiny and tender little sprout peeps its little head 

 through the soil, seeking the sunlight. A mighty 

 work before it is to build the great oak? Every mo- 

 ment must glow with infinite courage and patience. 

 But the tiny being is sufficient. Kissed by the 

 sunlight, refreshed by the dews, and fanned by the 

 breezes, cell after cell is added until, through days, 

 years and centuries, the giant of the forest stands 

 complete in stature. 



In multiplying to do all this work, the cells 

 differentiate into thousands of different species. 

 Each of these species forms, like microbes, many 

 colonies. All the multitude of colonies work, each 

 in its own way, some to build the bark of the 

 trunk, others its sap, others its heart, others its 



