The substance of the frond is made up by a single much-branched tube, with interwoven branches.
These branch, and may be packed or interwoven to form a very solid structure; but each grows in length independently of the others and retains its own individuality, though its growth in those types with a definite external form is of course correlated with that of its neighbors and is subject to the laws governing the general form of the body.
The different threads of social activity are so closely interwoven that we cannot follow any one for very long without forming wrong impressions, and it becomes necessary to turn back and study others which seemed at first sight unrelated to the subject of our investigations.
At the same time, the revolution in the means of transport and communication has destroyed, or is tending to destroy, local markets, and closely interwoven all the business of the world.
Superiorly the sheath either closely adheres to the muscular bodywall, with which it may even be partly interwoven, or it hangs freely in the connective tissue which fills the space between the intestine and the muscular body-wall.