12 WKEDS OF FARM LAND 



though a wild oat (Avena strigosa) is sometimes met with. 

 An examination of the Canadian weed flora is illuminat- 

 ing. Out of seventy of the worst agricultural weeds that are 

 fully described and figured by the Department of Agriculture l 

 forty-seven are characterised as being introduced from Europe, 

 one from Asia, and one from Tropical America, only twenty- 

 one being indigenous. 



Weed seeds may be carried from country to country, not 

 only among crop seeds, but also in ballast or with forage of 

 various kinds. An analysis of the flora of an old ballast heap 

 at Linnton, Oregon, on the Pacific coast, showed 2 thirty-two 

 species indigenous on the Pacific coast, eighty-eight species 

 introduced to the district but occurring elsewhere in Oregon, 

 and ninety three species collected only on the Linnton ballast 

 area and not found in other parts of the state. 



Probably 50 per cent, of the list of species cited by Nelson 

 have been collected for the first time on the Pacific coast, or 

 at least within the limits of the State of Oregon. If infor- 

 mation were available it would doubtless be found that a 

 similar state of affairs exists in other places where ballast is 

 dumped. In our own country much distribution is effected 

 by the carriage of waste dust and rubbish by railway to dumps 

 in various parts of the country. It is quite usual to find such 

 dumps colonised by plants which are not native to the locality, 

 but whose origin can be traced to the district from which the 

 waste material was brought. It is probable that a good deal 

 of weed distribution is effected in this manner, for if conditions 

 are suitable an introduced plant will quickly establish itself 

 and may become a troublesome pest. 



(<) Carriage in Manure. That weed seeds may be spread 

 by manure from an infested district is a danger whose reality 

 is too little recognised. If manure is stacked in a field 

 for some time prior to use it rapidly becomes covered 

 with weeds, among which fat hen (Chenopodium album) (Fig. 2) 

 and orache (A triplex patula) (Fig. 3) are often conspicuous. 

 The seeds of these plants and many others are transported in 

 the manure, which thus becomes a ready source of infestation. 

 Only too often the litter used for bedding cattle contains much 

 rubbish that is full of weed seeds, and unless excessive heat- 

 ing takes place many of these seeds retain their power of 



1 Clark, G. H., and Fletcher, J. (1909), " Farm Weeds of Canada ". 

 *Nel8on, J. C. (1917), ''The Introduction of Foreign Weeds in Ballast, as 

 illustrated by Ballast Plants at Linnton, Oregon," Torreya, XVII, pp. 151-160. 



