PERFECTION. 85 
consolidation of the substance of the Tree as new 
sap-wood each year adds to its circumference— 
the pith falling out of use, and oftentimes drying 
up, and the Tree secreting substances which help 
in the work of consolidating its woody matter. 
Meanwhile a beautiful office has been filled by 
the air passing into the leaves through the 
stomata, and thence at first down certain inter- 
stices called intercellular spaces, lying between 
the masses of cells, and on into the tissues of the 
Tree, helped in its progress, it is believed, by the 
spiral nature of the threads which are found in 
the tissues. With the sun’s light, acting from 
season to season upon the gaseous and fluid con- 
tributions to the life of the Tree, the whole of the 
wonderful work has been performed. Cylinder of 
sap-wood has been added to cylinder of wood ; 
new liber and bark have been successively formed 
to make room for the increased growth and bulk 
of the stem and branches. Hach year meanwhile 
the substance of the roots has been increasing. 
With the increase in bulk of the older roots, there 
has been augmentation in the number of foraging 
rootlets. Hosts of these have been annually 
