87 



Lappiila (leflexa Sonchus as per 



Polygonum aviculare Zea Mais 



Species occurring in 1917 onh': 

 Arctium minus Ranuncidtis acris 



Arenaria serpyllifolia Sisymbrium altissimum 



Brassica juncea Veronica arvensis 



Chrysanthemum Leiccanthemnm Veronica peregrina 



Dactylis glomerata Vicia villosa 



Hordeum juhatum 



Besides the change in the flora, still more striking develop- 

 ments were exhibited in the general appearance of the tract. 

 In 1915 the introduced species occurred as numerous but scattered 

 individuals onl}'. In 191 7 the premises of the camp and all the 

 logging roads were occupied by a meadow, in which Poapratensis, 

 Phleiim pratense and Agrostis alba were the dominant species, 

 with merely scattered colonies of other species. There were 

 numerous other individuals of introduced species along the walls 

 of the houses, at the edge of sawdust piles, and on rubbish heaps, 

 but the majority of foreign species were limited to a small number 

 of individuals scattered widely through the grass. 



It was indicated in the 1914 paper that introduced species are 

 characteristic of the logging roads forseveral years after they have 

 been abandoned. Their number is gradually reduced as the 

 growth of shrubs and young trees excludes the full sunHght. 

 But if the roads are used by farm wagons, thereby affording con- 

 tinual opportunities for fresh immigration, a foreign flora will 

 occur even in deep shade of the second-growth forest. 



IV. Method of Immigration 



In general, the immigration of all the introduced species de- 

 pends upon some form of human activities. The exceptions are 

 Verbascum Thapstcs, Lepidium virginicum, and Rumex acetosella, 

 which show some tendency to establish themselves among the 

 aspens at a distance from the roadsides, and Hieracinm auran- 

 tiacum, scattered colonies of which occur in moist ground. 



Travel in the uncultivated region is light, and limited almost 

 entirely to wagons. Dung from the horses is dropped along the 



