344 Annals of the Carnegie Museum. 



species, the latter being found attached to the old dead stems and 

 roots of the grass, and during damp periods often becoming quite 

 abundant. In the early stages of the dune Cakile may be present, 

 and in the later stages there is an increasing number of invaders from 

 the sand-plain, especially on the lower slopes of the dune. 



At Presque Isle the Ammophila dune, when finally surrounded by 

 sand-plain by the general advance of the shore-line, is either quickly 

 blown away, following the death of the grass, or else it passes quickly 

 into an Andropogon dune. 



As Ganong points out for the Miscou Beach, ''^ the Ammophila starts 

 in some accumulation of driftwood, which lying at the upper limit of 

 the drift-beach has had time to accumulate more or lesss and. Here 

 the Ammophila comes in, and, thriving best when partly covered with 

 freshly blown sand, begins the formation of a dune. In quiet sand 

 the grass dies in a very few years." 



To the west of the Light House Jetty the erosion of the beach was 

 stopped by the building of the jetty, and the beach has since been 

 growing lakeward, so that, instead of an abrupt cliff, there is now a 

 gentle slope towards the water. Back of the former sea-cliff and ex- 

 tending up to it is the white pine forest. Outside of the forest and 

 capping the crest of the present slope is a small area of the mixed 

 Myrica heath-formation in which are a few Pruims and Andropogon 

 dunes, and into this the pine forest is now advancing. The upper 

 half or two-thirds of the slope is occupied by the Ammophila forma- 

 tion essentially forming a fringing dune, but on account of the prox- 

 imity of the forest- and shrub-formations sand has continually filled in 

 back of the Ammophila dune, as rapidly as the latter has risen above 

 the level of the inclined plane of the slope. 



Outside of the true Ammophila zone, and extending from there down 

 to the Cakile-Xanthium formation of the drift-beach, there is a mixed 

 formation derived from the Ammophila- A\xw^ and the Panicum-Arte- 

 w/j-/(7-formations : 



Andropogon furcatus, Lathyrus jnaritiimis, 



Artemisia canadensis, Ammophila arenaria, 



Artemisia candata, Panicum virgatum, 



Populus deltoides. 



'1 Ganong, W. F. /. c, p. 88. 



"^Hitchcock, A. S. "Methods Used for Controlling and Reclaiming Sand- 

 Dunes." U. S. Dept. Agr., Bur. Plant Industry, Bull. 57: 14, 1904. 



