PLANTS THAT BUILD ISLANDS 123 
sea-beach panic-grass is very common. In the 
marshy salt lands we find salt-reed grass, creek- 
sedge, and numerous other reed-like grasses. The 
seaside blue-grass is, perhaps, more commonly used 
than any other kind, especially in the West. This 
is due to two reasons: because of its sand-binding 
qualities, and because of its excellence as grazing 
for cattle. In the South various kinds of sand- 
binders are used; chief among these are the well- 
known St. Augustine grass and seaside oats, which 
use their sand-collecting propensities to save the 
water-fronts. 
Occasionally an island is formed by a great piece 
of earth which has broken away from a low-water 
bank, usually near the mouth of a large river, and 
floated out to sea, the soil being held firmly together 
by matted grass roots. The sizes of these floating 
islands vary from a few feet in diameter to an 
area of several acres. Sometimes they carry only 
tiny crawling insects or no life at all; at other times 
there are trees and many small animals. Few of the 
islands exist long after they float out on to the 
rough waters of the ocean; but one or two have 
been known to travel many miles, resisting for 
months and even years all efforts of the waves to 
buffet them to pieces. 
Some islands rise out of the ocean, perhaps be- 
