86 



growth is also good, since the ground is covered with leaf mold 

 and is more retentive of moisture than the sand of the aspen 

 association. Nevertheless, the migration of the invaders is 

 closely dependent on human agency, and with one exception the 

 foreign species are not found away from the logging roads which 

 ramify through the forest. This exception is Hieracium aiiran- 

 tiacum, which is unusually mobile and is occasionally found at 

 some distance from a road. 



Lumbering is in progress during the winter, and the following 

 summer a considerable population of introduced species marks 

 every roadside, and is especially luxuriant in and near the logging 

 camp and stables. One tract of eighty acres, lumbered during 

 the winter of 1914-15, showed 41 introduced species in August, 

 1915,- together with 12 native species, characteristic of clearings 

 and burns. By 191 7, 16 of these had disappeared and 11 others 

 had arrived, leaving an introduced flora of 36 species, as listed 

 below. Species common to both years: 



Achillea millefolium 

 Agrostis alba 

 Brassica alba 

 Capsella bursa-pastoris 

 Cerastitim vidgatum 

 Chenopoditcm album 

 Cirsium arvense 

 Cirsium lanceolatum 

 Cynoglossum officinale 

 EchinocJiloa Crus-galli 

 Lepidium virginicum 

 Lychnis alba 

 Nepeta Cataria 

 Species occurring in 1915 only: 

 Amaranthus graecizans 

 Amaranthus retroflexus 

 Ambrosia artemisiifolia 

 Anthemis cotula 

 Avena saliva 

 Hieracium aurantiacum 



Phleum pratense 

 Plantago major 

 Poa annua 

 Poa compressa 

 Poa praiensis 

 Rumex acetosella 

 Rumex elongatus 

 Taraxacum officinale 

 Trifolium hybridum 

 Trifolium pratense 

 Trifolium repens 

 Verbascum thapsus 



Polygonum Convolvulus 

 Polygonum Persicaria 

 Setaria glauca 

 Silene noctiflora 

 Sisymbrium officinale 

 Solanum nigrum 



