84 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



limit, which is near the dead cedar trees, a rise and fall of about 

 1 8 inches. Occasional special high tides flood the lower stretches 

 of the cedar swamp and it is this that kills off the cedar. For 

 this tree is not a salt tolerant, while Nyssa and Qiierciis stellata, 

 inveterate inhabitants of the edges of most Long Island salt 

 marshes, flourish among the dead evergreens. 



It has recently been suggested by a geologist (23) that if along 

 the edges of salt marshes there were to be found a well-marked 

 zone of vegetation that seemed to be putting up a losing fight 

 against sea water, it would be excellent evidence that coastal sub- 

 sidence was well marked in the region. The reasoning seems to 

 be sound, especially for trees that are not good salt tolerants. It is 

 unlikely that such trees would become established if the amount 

 of salt water had in the past been unfavorable, but once having 

 reached maturity in a given situation, the question of the cause 

 of their death seems to force on one the necessity of accounting 

 for the obviously recent encroachment of the salt water. Such 

 seems to be the case at Merrick as plate io shows. 



Local conditions here made it easy to study the probable de- 

 velopment of the whole salt marsh. Extending out into the 

 marsh, just west of the area below the cedar swamp, is a long 

 promontory of higher land that reaches for nearly a mile towards 

 the bay. This lobe of drier land maintains a flora much like that 

 of the upland region of the coastal plain, except that the red 

 cedar, Juniperus virginiana, is the dominant tree. With scattered 

 plants of Quercus stellata, Acer carolinianum in lower parts, 

 Myrica carolinensis, Rhus copallina, a Vaccinium or two, and 

 Rosa Carolina, the bushes often tangled all together by Smilax 

 glauca, we pass by easy and rapid stages through thickets of 

 Baccharis and Iva to the open salt marsh which is quite bare of 

 woody vegetation. All these types may be found within twenty- 

 five feet of one another. The surface evidence of coastal sub- 

 sidence here is not convincing, for while this edge of the lobe of 

 higher land is much nearer the bay, no fringe of dead or dying 

 plants is to be found as in the case of the white cedar. The reason 

 too is obvious, as all the species above mentioned as inhabiting 

 the edges of the drier land, are good salt tolerants and not likely 

 to be affected by occasional inundations of sea water. 



It is unnecessary to review here all (he pros and cons of the 



