279 



The new growth decreases in size with increasing distance from the 

 center. Any accident received by the runners causes separation into 

 independent plants, from which new runners may extend. Pofen- 

 tilla can not contend with the wind. It is rather easily killed, either 

 by sand being blown away from its roots or by being buried in drift- 

 ing sand. In the spring, before there is a carpet of vegetation over 

 the ground, the young plants are to some extent protected from the 

 wind by the bushes of Salix syrticola and the dead stems of Juncus 

 halticus littorahs. Once a carpet is formed, there is little danger of 

 damage from the wind. 



If protected from wind and still connected with the parent plant, 

 runners may proceed through rifts in the Juncus, out upon the middle 

 beach, where they may develop roots and leaves in the usual way but 

 of smaller dimensions. During the season of 1908, when there was 

 an unusually small number of heavy winds, many long runners de- 

 veloped in this way. A number of them were severed, resulting in 

 the gradual starvation of the young plants, thus isolated upon the 

 middle beach. This was probably due to the deficiency of food ma- 

 terial there — a fact which has often been commented upon. The 

 season of 1909, with its heavy surf and strong wind storms, prevented 

 any such development of runners. 



The secondary species of this association are not many in either 

 number of species or of individuals. Without exception they arc 

 obviously under the usual size. This also is due to the lack of nour- 

 ishment in the sand. The commonest of these species is Juncus halti- 

 cus littoyaUs. A few J. alpimis insignis occur as relics where the Po- 

 tentilla has successfully invaded the Triglochin palustris association. 

 The Triglochin may also remain as a relic but it is less liable to per- 

 sist. 



LIST OF THE SPECIES OF THE POTENTILLA ANSERINA ASSOCIATION 



Dominant Species 

 Potentilla anserina 



Secondary Species 

 Juncus halticus litt oralis (which is also a relic) 



Relic Species 

 Juncus alpinus insignis Triglochin palustris 



Invading Species 

 Salix syrticola Populus dcltoidcs (1-2 dm. high) 



Calamovilfa longifolia Salix longifolia 



Panicuni lirgatujii 



