Small peninsulas are known as promontories or headlands, and the extremity as a cape.
Numerous small archipelagoes and islands, of which the chief are Belle Tie, Groix and Ushant, fringe the Breton coast.- North of the Bay of St Michel the peninsula of Cotentin, terminating in the promontories of Hague and Barfleur, juts north into the English Channel and closes the bay of the Seine on the -west.
Cherbourg, its chid harbour, lies on the northern shore between the two promontories.
Many of the Aegean islands, or chains of islands, are actually prolongations of promontories of the mainland.
The significance of these phenomena, which present many minor modifications in different cases, is nol fully understood, but one purpose of the formation of phloem promontories and islands seems to be the protection of the sieve-tubes from crushing by the often considerable peripheral pressure that is e~ercised on the stems of these lianes.