1178. How are the seeds of the mistletoe transferred from its own stem to the bark of trees?
Various birds, and particularly the missel thrush, feed upon the berries. As the bird moves in pursuit of its food, the viscid berries attach themselves to its feathers, and in this way the thrush is the instrument which conveys the seed to the spot to which it adheres, and from which the tree ultimately grows.
1179. What is the circulation of the sap in plants?
The circulation of the sap is the movement of the nutritive juices by which the plant is sustained. There is a slow uninterrupted movement of the sap from the root through the stems to the leaves, and downwards from the leaves through the bark to the root.
"For the sun is no sooner arisen with a burning heat, but it withereth the grass, and the flower thereof falleth, and the grace of the fashion of it perisheth: so also shall the rich man fade away in his ways."—James i.
1180. Why does the sap of plants thus ascend and descend?
Because it conveys upward from the ground some of the matter by which the plant is to be nourished, and which must undergo digestion in the leaves; and it brings downward from the leaves the matters absorbed, for the nourishment of the plant, and discharges through the root the substances which the plant cannot use.
The movement of the sap is most active in the spring; but in the depths of the winter it almost ceases.