Development of the Vegetation of New York State 103 
a stiff clay, or clay and gravel forms this substratum as may 
happen where the normal contour permitted a high ground- 
water level, then such firmness is assured, but if and this 
is particularly the case we are supposing — the substratum 
is a built-up bed of soft muck then it is soft and miry, even 
loose ooze, under shallow water. In this case it is especially 
necessary for the plant to construct a firm base. Or to put 
the matter differently, the plant society is limited to growth 
forms which, in the first place, can tolerate a submerged or 
water-soaked soil of organic stuff, and in the second place, 
possess a habit of growth calculated to construct a firm mat 
or tussock. If you happen to have tried to cut a block of 
eat-tail mat from the marsh or to cut through a sedge tussock 
or pull up or dig out a tussock of royal fern, you have gained 
a fine appreciation of the effectiveness with which marsh 
plants firm the soil. You have found a firm, tough, fibrous 
mass made up of innumerable root fibres, rhizomes, and the 
bases of living and dead shoots. See Fig. 6. 
Cat-tail Marshes. 
In New York extensive cat-tail marshes are very obviously 
associated with the early stages of land emergence and upon 
close examination of the substratum they are just as 
obviously the agency in consummating this. Striking illus- 
trations of this are furnished by the marshes of the Long 
Island coast and of the lower Hudson where low flats have 
been built up above or barred against tidal flooding. The 
Hackensack Meadows on the New Jersey side are perhaps 
the most widely known instance. Again, the shores of Lake 
Ontario — see topographic sheets of Pulaski, Rochester and 
Ontario Beach quadrangles respectively — offer even clearer 
if more limited areas of this young land building under cat- 
tail mats. The cases are those where a small bay — in the 
ease of Irondequoit Bay much larger and less advanced in 
filling —has been cut off from the lake by a beach-sand 
barrier leaving a narrow opening for the discharge of flood 
waters of the stream whose valley, opening upon the lake, 
determined the extent of the bay so eut off by the barrier. 
