158 



HENRY ALLAN GLEASON 



shown in table 8. If the development of the surrounding forest 

 is restricted by further clearing or by fire, the blue grass associa- 

 tion probably continues indefinitely. 



TABLE 7 



Development of blue grass association. Frequency indices based on 15 two-meter 



quadrats 



Poa pratensis 



Pteris aquilina 



Verbascum thapsus 



Chenopodium album 



Sisymbrium altissimum 



Erigeron canadensis 



Polygonum convolvulus 



Taraxacum officinale 



Setaria glauca 



Rubus idaeus, var. aculeatissi- 



mus 



Aralia hispida 



Secale cereale 



Lepidium virginicum 



Rhus glabra 



Prunus pennsylvanica 



Triticum sativum 



Epilobium angustifolium 



Agrostis alba 



Amaranthus retroflexus 



Apocynum androsaemifolium. 



Capsella bursa-pastoris 



Fagopyrum esculentum 



Gnaphalium decurrens 



Solidago canadensis 



1914 1917 



27 

 13 

 13 

 20 



7 

 7 

 7 

 7 

 7 

 7 

 

 



0* 

 13 

 7 

 

 7 

 

 

 

 

 

 7 

 7 



*Present in the association but not in the quadrats counted. 



TABLE 8 



Development of blue grass association. Frequency indices based on 15 two-meter 



quadrats 



Poa pratensis 



Erigeron canadensis 



Rubus idaeus, var. aculeatissi- 



mus 



Verbascum thapsus 



Chenopodium album 



Polygonum convolvulus , 



Lepidium virginicum 



Sisrjmbrium altissimum 



Gnaphalium decurrens. . . 



Agrostis alba 



Epilobium angustifolium. 

 Amaranthus blitoides. . . . 



Aralia hispida 



Panicum capillar e 



Prunus pennsylvanica . . . 

 Sambucus racemosa 



1914 1917 



20 

 13 

 13 



7 

 7 

 7 

 7 

 7 





 



7 

 

 7 

 

 7 

 0* 



*Present in the association but not in the quadrats counted. 



Additional species present in the association in 1917, but not in the quadrata 

 counted, and not present in 1914: Acer saccharum seedlings, Phleum pratense, 

 Pteris aquilina, Rhus glabra, Rubus allegheniensis, Solidago canadensis, Taraxa- 

 cum officinale. 



