204 NINETEENTH REPORT. 



Border Zone Formation. Where tlie climax forest, still untouched, 

 extends to the shore, a zone 50 to 100 yards in width, shows a very 

 characteristic difference in species. (Plate IX.) The trees are Thuja, 

 Ostrya, Tilia, and Abies balsamea, with Celastrus scandens. The line 

 of demarcation is not sharp, but the climax trees, especially hemlock, 

 mingle with the others almost to the edge of the cliffs. The characteristic 

 border zone species are not found farther back in the climax forest. 



B. Dune Complex Vegetation. On the open dune complex there are 

 found a number of forest patches, apparently growing in valleys between 

 former fixed dunes whose summits have been entirely blown away. 

 (Plate X.) The interiors of these patches present all the characteristics 

 of a heavy forest, and their evaporation rate is almost as low as that 

 of the climax forest. But the vegetation is characteristic of the border 

 zone described above, containing especially Thuja and Abies, and is 

 marked by some trees reaching two feet in diameter, but not over 30 

 feet in height. The undergrowth is similar to that of the climax forest, 

 but is especially characterized by Viburnum acerifolium, Rhus toxi- 

 codendron, and Aralia nudicaulis. On the edges, next to the open sand, 

 are found Arctostaphylos, Linnaea and Juniperus horizontals. These 

 apparently originate in the fixed area, and extend out on to the sand, 

 forming a protective covering, which frequently contains also Juniperus 

 communis. Buried trees and occasional graveyards are to be found all 

 over the moving sand area. 



There is not much forest reproduction on the moving sand, and, unlike 

 some similar regions, no young stands of Pinus Banksiana, nor any 

 Cottonwood dunes similar to those of the Indiana-Michigan region. There 

 are practically no i)anne colonies, but a few isolated oval groups, chiefly 

 of Thuja and Betula alba, which seem to have originated from pannes, 

 growing upward as the sand accumulates around their stems. A few 

 other patches have reached the low conifer stage, but seem to have been 

 chiefly invasions from the relic patches previously described. On the 

 open sand the vegetation consists of characteristic pioneer herbs, 

 Ammophila and Calamovilfa among grasses, with I^athyrus maritima, 

 Artemisia, Campanula rotundifolia, Cirsium Pitcheri, some Hudsonia, and 

 Zygadenus chloranthus. There are frequent mounds protected by 

 Calamovilfa, Primus pumila, Salix syrticola, and Cornus stolonifera. 



The growth of grasses, especially Ammophila, is quite extensive, and 

 frequently approaches the character of fixed grass dunes. This is 

 especially noticeable on the advancing lee slopes, where the complex is 

 overwhelming the climax forest. 



C. Vegetation of the Crater Group. This group apparently con- 

 sisted at -first of fixed dunes which were at least partly covered by the 



