426 BOTANICAL GAZETTE [may 



could account for this encroachment, and I beheve the latter more 

 probable. The erosive force might well have been wind, acting 

 subsequent to the removal of the white pine forest which evidently 

 existed here. High tidal action has undoubtedly cooperated in the 

 removal of the upper part of what appears to have been an extensive 

 sand plain, as indicated by the north and south extensions of the 

 lagoons. 



Restoration of original condition 



Within a century it seems probable that an area somewhat more 

 extensive to the south than that now occupied by the salt marsh, 

 and lying in the lee of the highlands to the north, was covered with 

 a stand of Pinus Strobus. The present area of the dune complex, 

 lacking this protection from marine influences, was covered with a 

 stand of Picea canadensis and Abies, and this stand extended in 

 its full width to the present end of the spit. It seems probable that 

 the dune complex is a relatively recent phenomenon, developing 

 subsequent to the removal of the stand of white pine. At about 

 this same time the channel of the tidal current was changed and 

 began cutting at the south end of the spit, eroding the Picea stand 

 (fig. 5). According to a native, about one-third of this erosion has 

 been accomphshed in the last 35 years, or at the rate of 25 ft. per 

 annum. If this rate has been approximately constant, the Picea 

 stand was intact within a century to the end of the spit, which 

 now lies bare for about one-half mile (fig. 3). 



Summary 



It is the purpose of this paper to put on record several facts of 

 ecological interest: (i) a coniferous sand dune with Picea cana- 

 densis as its facies located at the latitude of 47° north; (2) Poa 

 compressa as a sand binder; (3) abundant layering in Picea 

 canadensis and Abies balsamea; (4) the anomalous condition of a 

 sand dune moving seaward; (5) a phenomenal development of 

 Arceuthobiiim pusillum on Picea canadensis; (6) the decisive value 

 of ecological data in the interpretation of physiographic phenomena. 



Western State Normal School 

 Kalamazoo, Mich. 



