Jennings : A Botanical Survey of Presque Isle. 395 



ing of the board-walk running over to the lighthouse. The vegeta- 

 tion of this area now consists of a secondary formation which may be 

 termed the 



Popiilus-Rhus Secondary Formation. 

 This formation is considerably mixed with various adjacent forma- 

 tions, but its general structure is as follows: 

 Fades. — 



Populus tremuloides, Rhus typhina. 



Secondary Species. — 



Andropogon furcatiis , Panicum scribneriamim, 



Danthonia spicata., Agrostis hyemalis, 



Poa triflo7-a, Poa compressa, 



Rubus a/iegheniensis, Ritbiis villosus, 



Prunus virginiana, Primus serotina, 



Celastrus scandens, Acer saccharinum, 



Koellia verticillata, Gnaphaliuvi polycephalum, 



Gnaphaliuin uliginosum, Pinus strobus, 

 Myrica carolinensis, Quercus borealis, 



Quercus velutina, Sassafras sassafras, 



Aleibomia dillenii, Prunus pcnnsylvanica^ 



Prunus puini la, Tilia americana, 



Leptilon canadense, Artemisia canadensis, 



Erechtites hieracifolia. 

 No species among the long list of secondary species could with 

 propriety be designated as "principal species." The larger part of 

 , the vegetation is comprised in the Populus tremuloides consocies, this 

 being of much larger extent than is the Rhus typhina consocies. The 

 two facies are rarely found closely associated, but are in separate 

 clumps, or in the absence of Rhus, the Populus occurs singly, scattered 

 about among the secondary species. 



After the normal vegetation was destroyed, there was evidently con- 

 siderable shifting of the sand by the wind, and some dune building, 

 this latter process leading to the invasion of the area by certain dune- 

 plants, some of which (^Prunus pumila, Andropogon furcatus) still 

 persist among the so-called secondary species. 



As the matter now stands with reference to the secondary species 

 the PopuluS'Rhus formation is being invaded by various formations of 

 both the sand-plain, the ridge, and the dune successions. There are, 



